Latest ESO telbib papers

Featureless stars: flux calibration for extremely large telescopes

First Author: Cooke, Ryan J.
Instruments: XSHOOTER
ProgramIDs: 111.24LB
BibCode: 2026MNRAS.546f2246C

The spectrophotometric flux calibration of recent spectroscopic surveys has reached a limiting systematic precision of approximately

$1-3$

per cent, and is often biased near the wavelengths associated with H I Balmer absorption. As we prepare for the next generation of imaging and spectroscopic surveys, and high-precision cosmology experiments, we must find a way to address this systematic. Towards this goal, we have identified a global network of 29 bright (

$G< 17.5$

) featureless white dwarf stars that have a spectral energy distribution consistent with an almost pure blackbody form over the entire optical and near-infrared wavelength range. Based on this sample, we have computed the systematic uncertainty and AB magnitude offsets associated with Gaia, SDSS, SMSS, Pan-STARRS, DES, and 2MASS, and we have also checked the consistency of our objects with both GALEX and WISE. The magnitude range of the featureless stars reported here are ideally suited to observations taken with the forthcoming generation of extremely large telescopes, as well as calibrating the survey data acquired by the Rubin, Euclid, and Roman observatories. Finally, all of the high-precision spectrophotometric standard stars reported here have been included in the latest release of the PYPEIT data reduction pipeline.

E-XQR-30: evidence for an increase in the ionization state of metal absorbers from z ∼ 6 to z ∼ 2

First Author: Rowlands, Stephanie
Instruments: XSHOOTER
ProgramIDs: 0102.A-0154, 0102.A-0478, 084.A-0360, 087.A-0607, 088.A-0897, 098.B-0537, 1103.A-0817, 294.A-5031, 60.A-9024, 096.A-0095, 096.A-0418, 097.B-1070, 086.A-0574, 086.A-0162, 085.A-0299, 084.A-0390, 084.A-0550, 0101.B-0272, 0100.A-0625
BibCode: 2026MNRAS.546f2254R

We investigate the evolution of the ionization state of metal-enriched gas in and around galaxies near the epoch of reionization using a sample of 488 metal absorption systems at 4.3

$\lesssim z \lesssim$

6.3 from the E-XQR-30 survey. We classify the absorption systems based on whether they display only low-ionization absorption (C II, Si II, Mg II), only high-ionization absorption (C IV, Si IV), or both. The percentage of low-ionization-only systems decreases from 24 per cent at

$z\sim$

6 to 2 per cent at

$z\sim$

4.3, whilst the fraction of high-ionization-only systems increases from 52 per cent to 82 per cent. For mixed absorbers (with both low and high ionization absorption), we use the column density ratios log(N_{C II}/N_{C IV}) and log(N_{Si II}/N_{Si IV}) to quantify the average ionization as a function of redshift. The log(N_{Si II}/N_{Si IV}) ratio does not change significantly over 5

$\lesssim z \lesssim$

6.3. We combine the E-XQR-30 log(N_{C II}/N_{C IV}) measurements with literature measurements at

$z\sim$

2─4 and find that the log(N_{C II}/N_{C IV}) ratio declines by a factor of

$\sim$

20 between

$z\sim$

6 and

$z\sim$

2. To explore possible drivers of this evolution, we run photoionization models of gas slabs illuminated by a uniform ultraviolet (UV) background at fixed density, metallicity, and H I column density. We find that the increase in the ionization state of metal absorbers towards lower redshifts can likely be explained by some combination of (1) an increase in the metallicity of C IV-absorbing gas and (2) a decrease in the typical H I column densities of the absorbing gas, driven by the declining cosmic mean density and a rapid rise in the strength of the UV background during the final stages of reionization.

JWST Exoplanetary Worlds and Elemental Survey (JEWELS). I. High-precision Chemical Abundances of 20 FGK Planet-hosting Stars from JWST Cycle 2

First Author: Sun, Qinghui
Instruments: ESPRESSO, HARPS, UVES
ProgramIDs: 106.21QM, 192.C-0224, 099.C-0491, 0102.D-0789, 198.C-0169, 084.C-1039, 099.C-0303, 1102.C-0923, 0103.C-0874, 082.C-0040, 0103.C-0422, 0102.C-0493, 097.C-0863, 095.D-0383, 0102.D-0185, 089.D-0202, 112.25T7, 111.24HZ, 112.25T4, 105.20KD, 106.21BV
BibCode: 2026ApJS..282...37S

We present high-precision chemical abundances for 20 FGK stars hosting planets observed in JWST Cycle 2 GO programs. Using high-resolution, high-signal-to-noise ratio spectra from the ESO and Keck archives, we perform a strict line-by-line differential analysis relative to the Sun to derive stellar parameters and abundances of 19 elements from C to Zn. The stars span effective temperatures of 4500─6500 K and metallicities from −0.57 to +0.50 dex. The sample includes hosts of both gas giants and terrestrial planets, allowing direct comparison between stellar composition and planetary properties. Several of the giant planets orbit metal-rich stars. The detailed abundance patterns show clear chemical diversity, including carbon-enhanced but mildly metal-poor stars (TOI-824, TOI-561, TOI-1130, GJ 9827) and α-enhanced metal-poor stars (TOI-561, GJ 9827, TOI-824). These variations trace differences in protoplanetary disk composition and may influence planetary interiors and atmospheric chemistry. The planet hosts show a range of [C/O] ratios, and the diverse [Mg/Si] ratios may suggest varied interior compositions for their rocky planets. This homogeneous stellar abundance, together with future uniform JWST planetary atmosphere measurements, provides a foundation for exploring the planet mass─metallicity relation and the connection between stellar chemistry and planetary formation pathways. These results constitute the first step in a larger survey spanning multiple JWST cycles to systematically examine how host star composition shapes exoplanetary systems.

Abundance of Heavy r-process Elements in CEMP-rs Stars: The Role of the i-process

First Author: Riyas, A. M.
Instruments: UVES
ProgramIDs: 105.20LJ, 076.D-0451, 078.D-0217
BibCode: 2026ApJ...997...44R

Carbon-enhanced metal-poor (CEMP) stars are ancient stars enriched in carbon and heavy elements. Some of these stars exhibit enhanced s-process and/or r-process elements, and hence are classified as CEMP-s, CEMP-rs, or CEMP-r. This classification is challenging due to the limited availability of heavy element abundances, particularly among r-process elements. Heavy r-process elements such as terbium, holmium, thulium, ytterbium, lutetium, tantalum, and iridium have rarely been measured because their sensitive lines are located in the ultraviolet. However, they provide sensitive diagnostics of the s-, r-, and i- nucleosynthetic processes. In this work, we aim to obtain a secure classification of CEMP-s and -rs stars and investigate whether the i-process can account for the measured abundance patterns in CEMP-rs stars. We derive the abundance profiles, notably for 12 heavy r-elements, including, in some cases, tantalum, using high-resolution UVES spectra of 17 CEMP-s and -rs stars. Based on indicators such as the [s/r] abundance ratio or the model-independent "abundance distance", nine stars are confirmed as CEMP-rs and six as CEMP-s. The classification of two objects remains uncertain. The i-process satisfactorily reproduces the abundance patterns of CEMP-rs stars. However, larger samples are needed to confirm trends with metallicity and clarify how CEMP-rs stars differ from CEMP-s stars.

Secondary Standards in the UKIRT Faint Standard Fields

First Author: Górski, Marek
Instruments: SOFI
ProgramIDs: 190.D-0237, 095.D-0424, 092.D-0295, 090.D-0409, 084.D-0591, 094.D-0056, 099.D-0307, 0102.D-0590, 084.D-0640, 097.D-0151, 088.D-0447, 088.D-0401, 0102.D-0469, 096.D-0170, 092.D-0349, 082.D-0513
BibCode: 2026ApJS..282...44G

We present precise J- and K-band photometric measurements for 128 near-infrared (NIR) secondary standard stars, located in the 19 United Kingdom Infrared Telescope/Maunakea Observatories (UKIRT/MKO) primary faint standard fields. The data were collected over more than 50 nights, covering a decade of observations between 2008 and 2018 at the ESO La Silla Observatory, using the New Technology Telescope equipped with the SOFI NIR camera. Presented magnitudes are calibrated onto the MKO photometric system. The J- and K-band magnitudes range from 10 to 15.8 mag, with median values of J∼ = 13.5 mag and K∼ = 13 mag. The selection process ensured high photometric quality, with a precision better than 0.01 mag for all stars. The catalog excludes stars with close neighbors, high proper motion, or variable stars. Using these fields for standardization can improve the precision and accuracy of photometric calibrations without increasing the observational time cost.

ExoJAX Retrievals of VLT/CRIRES Spectra of Luhman 16AB: C/O Ratios and Systematic Uncertainties

First Author: Yama, Hibiki
Instruments: CRIRES
ProgramIDs: 291.C-5006
BibCode: 2026ApJ...997..118Y

We present atmospheric retrievals of the benchmark brown dwarf binary Luhman 16AB using high-resolution VLT/CRIRES spectra and the differentiable framework ExoJAX. We derive elemental abundances and temperature─pressure (T─P) profiles while explicitly testing the robustness of the results against major sources of systematic uncertainty. We first perform retrievals with a power-law T─P profile and assess the sensitivity of inferred molecular abundances and C/O ratios to different CO line lists (ExoMol, HITEMP with air- and H2-broadening). We then introduce a flexible Gaussian process-based T─P profile, allowing a nonparametric characterization of the thermal structure and a more conservative treatment of uncertainties. For both components, we infer C/O ratios of about 0.67, slightly above solar, with line list systematics at the 7% level emerging as the dominant source of uncertainty, whereas assumptions about T─P parameterization or photometric variability play a lesser role. The retrieved T─P profiles and molecular abundances are broadly consistent with atmospheric models and equilibrium chemistry. Our results establish Luhman 16AB as a key anchor for substellar C/O measurements, demonstrate the utility of flexible T─P modeling in high-resolution retrievals, and highlight the importance of systematic tests—particularly line list uncertainties—for robust comparisons between brown dwarfs and giant exoplanets.

Interferometric view into RT Pav's long secondary period: Binary versus oscillatory convective modes

First Author: Courtney-Barrer, B.
Instruments: GRAVITY, MATISSE, PIONIER
ProgramIDs: 109.23K5
BibCode: 2026A&A...705A.187C

Context. Long secondary periods (LSPs) occur in roughly one third of evolved stars, yet their origin remains uncertain. Two leading hypotheses are oscillatory convective modes and a binary companion enshrouded in dust. Aims. We investigate the LSP in the red giant RT Pav using multiwavelength interferometry to test these competing hypotheses. Methods. Observations of RT Pav were obtained with the VLTI instruments PIONIER, GRAVITY, and MATISSE spanning 1.5─5.0 μm, near the expected phase of maximum projected separation under a binary hypothesis. These data were complemented by photometric data and Gaia DR3 astrometry to constrain companion mass, orbital geometry, and photometric amplitude. Monte Carlo simulations evaluated expected interferometric signatures under both scenarios. Parametric models, including uniform-disk, limb-darkened, uniform-ellipse, binary, and oscillatory convective dipole representations, were fitted to squared-visibility and closure-phase data, informing image reconstructions. Results. Gaia constrains any potential companion to a mass whose Roche-lobe volume is smaller than the minimum extent required by the observed photometric modulation, implying that any obscuring or scattering region capable of producing the observed variability would lie beyond the gravitationally bound zone of such a companion. Binary models often return the lowest χ_ν², yet fitted positions are not consistent across wavelength, closure phases do not increase with wavelength as a dusty companion would predict, and we only find significant (> 3σ) detections occurring in two of the four tested instrumental wavebands, which is inconsistent with a coherent companion signal. Furthermore simulations and theoretical estimates indicate that a companion with a ∼1% flux ratio, at LSP-consistent separations should be consistently detectable (near or above our 3σ limits) for standard O-rich asymptotic giant branch (AGB) dust via scattering and/or thermal emission, which is not found. Conversely, an oscillatory convective dipole with a ∼200 K temperature contrast reproduces the H band morphology and the visible light-curve amplitude without violating Gaia or photometric constraints. Finally, significant short wavelength companion signals are completely removed when fitting the residuals of the best fit dipole model. Conclusions. Our interferometric snapshot of RT Pav, acquired near the phase of maximum projected separation under the binary hypothesis, supports oscillatory convective modes as the most physically consistent explanation for its LSP. A logical next step will be time-resolved spectro-interferometric monitoring across the LSP cycle.

ALMAGAL: VI. The spatial distribution of dense cores during the evolution of cluster-forming massive clumps

First Author: Schisano, E.
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00195.L
BibCode: 2026A&A...707A.221S

Context. High-mass stars and star clusters form from the fragmentation of massive dense clumps driven by gravity, turbulence, and magnetic fields. The extent to which each of these agents impacts the fragmentation depending on the clump mass, density, and evolutionary stage is still largely unknown. Aims. The ALMA evolutionary study of high-mass protocluster formation in the GALaxy (ALMAGAL) project, with ∼1000 clumps observed at ∼1000 au resolution, allows a statistically significant characterization of the fragmentation process over a large range of clump physical parameters and evolutionary stages. Our goal is to characterize where and how the dense cores revealed by ALMA are distributed in massive potentially cluster-forming clumps to trace how fragmentation is initially set and how it proceeds before gas dispersal due to stellar feedback. Methods. We characterized the spatial distribution of dense cores in the 514 ALMAGAL clumps that host at least four cores, using a set of quantitative descriptors that we evaluated against the clump bolometric luminosity-to-mass ratio, which we adopted as an indicator of the evolution of the system. We measured the separations between cores with the minimum spanning tree (MST) method, which we compared with the predictions of gravitational fragmentation from Jeans theory. We investigated whether cores have specific arrangements using the Q parameter or variations due to their masses with the mass segregation ratio, Λ_MSR. Results. ALMAGAL cores are distributed throughout the entire area of the clump, usually arranged in elliptical groups with an axis ratio e ∼2.2, although high values with e ≥ 5 are also observed. We found a single characteristic core separation per clump in ∼76% of cases, suggesting that multiple fragmentation lengths may be frequently present. Typical core separations are compatible with the clump-averaged thermal Jeans length, λ_J^th. However, we found an additional population of cores, typical of low-fragmented and young clumps, which are on average more widely separated with l ≍ 3 × λ_J^th. By stacking the distributions of the core separations in clumps of similar evolutionary stage, we also found that the separation decreases on average from l ∼22 000 au in younger systems to l ∼7000 au in more evolved ones. The ALMAGAL cores are typically distributed in fractal-type subclusters, while centrally concentrated patterns appear only at later stages, but we do not observe a progressive transition between these configurations with evolution. Finally, we also found 110 ALMAGAL systems with a signature of mass segregation, with an occurrence that increases with evolution.

Investigating the Nested Structure of the Outflow from the Low Luminosity Protostar IRAS 16253-2429 Using JWST and ALMA

First Author: Narang, Mayank
Instruments: ALMA_Band_6
ProgramIDs: 2019.A.00034.S, 2019.1.00261.L
BibCode: 2026ApJ..1000..184N

Understanding the earliest stage of star and planet formation requires detailed observations to address the connection and interplay between the accretion, outflow, and disk evolution. We present results from the observations of the low luminosity (L_bol ∼ 0.2 L_⊙) and mass (M_* ∼ 0.15 M_⊙) Class 0 protostar IRAS 16253−2429, conducted as part of the eDisk Atacama Large Millimeter/submillimeter Array (ALMA) large program and the JWST cycle-1 GO Investigating Protostellar Accretion program. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at ≤5 μm), with a brighter, extended northern side. We detect 15 pure rotational H₂ transitions (E_up: 1015─21411 K), revealing a wide-angle molecular outflow. The outflow width (as traced in H₂ 0─0 S(11)) at the protostellar location measures ≤35 au, slightly larger than the dust and Keplerian disk diameters (∼30 au) but wider than the 20─23 au jet width in [Fe II]. The opening angle narrows from 40° to 35° for the low-J H₂ lines (up to S(5)) and the cold gas component (ALMA ¹²CO) to ∼28°─19° for the high-J H₂ lines (S(7)─S(11)). Position─velocity diagrams of H₂ reveal higher velocities for higher E_up, ranging from 12.5 km s⁻¹ for H₂ 0─0 S(1) and S(2) to 28.5 km s⁻¹ for H₂ 0─0 S(5) and S(7) with respect to the mean flow velocity. The nested excitation and velocity structure of the collimated jet and wide-angle wind suggest a magnetohydrodynamic wind as a likely launching mechanism, similar to the findings in other protostars and Class II sources. The lower velocity millimeter CO may be gas from the infalling envelope accelerated outwards by the wide-angle wind along the cavity walls.

Benchmarking pre-main sequence stellar evolutionary tracks using disk-based dynamical stellar masses

First Author: Zallio, Luigi
Instruments: ALMA_Band_6, ALMA_Band_7, XSHOOTER
ProgramIDs: 115.27XL, 113.26NN, 097.C-0378, 105.2082, 0101.C-0866, 2013.1.00395.S, 2018.1.00564.S, 2012.1.00688.S, 2011.0.00526.S
BibCode: 2026A&A...708L...1Z

Stellar masses are a fundamental property to understand models of pre-main sequence evolution, but their values derived from Hertzsprung─Russell (HR) diagrams are strongly model dependent. We benchmark pre-main sequence stellar evolutionary tracks using stellar masses dynamically estimated by fitting a parametric model to ALMA observations of the ¹²CO (J = 3 − 2) line transition emitted by the disks orbiting 20 sources in the old (4 − 14 Myr) Upper Scorpius star forming region. We derive stellar masses from HR diagram fitting for ten different stellar evolutionary models, which we then compare with their stellar dynamical masses for comparison in the stellar mass range 0.1 − 1.3 M_⊙. Models with a moderate-to-low fraction of cold stellar spots (f = 17%) most accurately reproduce the dynamical stellar masses (100% of the targets agree within ±1σ). While a higher spot coverage (f = 34%) provides similar stellar mass predictions similar to magnetic equipartition models, larger fractions (f ≥ 51%) significantly disagree with dynamical masses. Magnetic equipartition models overestimate stellar masses up to a factor ∼20%, whereas non-magnetic models underestimate them up to ∼12%. For some models, there is evidence that the stellar mass discrepancies are anticorrelated with dynamical stellar masses. When stellar dynamical mass priors are considered in HR diagram fitting, the median age of a single source can change up to ∼25%, while the median ages inferred across different tracks become consistent, with the age scatter decreasing by ≳77%. These results provide strong empirical constraints for testing and developing evolutionary models of pre-main sequence stars.

WISDOM Project ─ XXVII. Giant molecular clouds of the lenticular galaxy NGC 1387: similarities with spiral galaxy clouds

First Author: Liang, Fu-Heng
Instruments: ALMA_Band_6, MUSE
ProgramIDs: 296.B-5054, 2016.1.00437.S, 2016.2.00053.S
BibCode: 2026MNRAS.547ag221L

Molecular gas is crucial to understanding star formation and galaxy evolution, but the giant molecular clouds (GMCs) of early-type galaxies (ETGs) have rarely been studied. Here, we present analyses of the spatially resolved GMCs of the lenticular galaxy NGC 1387, exploiting high spatial resolution (

$0.15\ \mathrm{ arcsec}$

or 14 pc)

$^{12}$

CO(2-1) line observations from the Atacama Large Millimeter/submillimeter Array. We identify 1285 individual GMCs and measure the fundamental properties (radius, velocity dispersion, and molecular gas mass) of each with a modified version of the CPROPStoo package. Unusually for an ETG, the GMCs of NGC 1387 follow scaling relations very similar to those of the Milky Way disc and Local Group galaxy clouds, and most are virialized. GMCs with large masses and radii and/or small galactocentric distances have their angular momenta aligned with the large-scale galactic rotation, while other GMCs do not. These results show that ETGs have more diversified GMC properties than previously thought. We discuss potential reasons for such diversity, and viewing-angle dependency is a plausible candidate.

MIRACLE: II. Unveiling the multiphase gas interplay in the circumnuclear region of NGC 1365 via multicloud modeling

First Author: Ceci, M.
Instruments: ALMA_Band_7, MUSE
ProgramIDs: 094.B-0321, 2016.1.00296.S
BibCode: 2026A&A...707A.376C

We present a multiphase analysis of the gas in the circumnuclear region (∼0.9 × 0.9 kpc²) of the nearby barred Seyfert 1.8 galaxy NGC 1365, observed as part of the Mid-IR Activity of Circumnuclear Line Emission (MIRACLE) program. Specifically, we combined spatially resolved spectroscopic data from JWST/MIRI, VLT/MUSE, and ALMA to provide a multiphase characterization of the ionized atomic and the warm and cold molecular gas phases. MIRI data enabled the detection of more than 40 mid-IR emission lines from ionized or warm molecular gas. Moment maps show that both cold and warm molecular gas trace the circumnuclear ring, following the rotation of the stellar disk. The ionized gas exhibits flux distributions and kinematics that vary depending on the ionization potential (IP). Low-IP species (≤25 eV) mainly trace the rotating disk, while higher-IP species (up to ∼120 eV) trace the outflowing gas. Both [O III] λ5007 Å and [Ne V] λ14 μm trace the nuclear outflow cone toward the southeast. In addition, the [Ne V] λ14 μm line traces the counter-cone of the outflow to the northwest, which is obscured in the optical at these circumnuclear scales, and is thus undetected in [O III] λ5007 Å. Unlike optical diagnostics, spatially resolved mid-IR diagnostics reveal the key role of the active galactic nucleus (AGN) as the source of gas ionization in the central region. We derived the electron density from the [Ne V] λ24 μm/[Ne V] λ14 μm line ratio, finding a median value of (750 ± 440) cm⁻³, consistent with previous estimates obtained from the optical [S II] doublet. Lastly, we applied, for the first time, a fully self-consistent combination of state-of-the-art photoionization and kinematic models (HOMERUN + MOKA^3D) to estimate the intrinsic physical outflow properties, kinematics, and energetics ─ overcoming the limitations of classical methods based on oversimplified assumptions. Exploiting the unprecedented synergy between JWST/MIRI and VLT/MUSE, HOMERUN allows us to simultaneously reproduce the fluxes of over 60 emission lines spanning from the optical to the mid-IR. This unique approach enables us to disentangle the physical conditions of AGN- and star formation-dominated components and robustly estimate the mass of the outflowing gas and other physical properties.

Young system development in a cometary globule: An investigation into the eccentric disk around AT Pyx^* in terms of planet formation and interaction with its surrounding environment

First Author: McLachlan, D.
Instruments: ALMA_Band_6, ESPRESSO, SPHERE, XSHOOTER
ProgramIDs: 111.24UB, 112.25B7, 099.C-0147, 112.25BZ, 2021.1.01705.S
BibCode: 2026A&A...707A.379M

Context. To understand the formation of planetary systems, it is necessary to observe and study systems at different evolutionary stages and in different environments. This paper presents new data and analyses of the AT Pyx system, a disk-hosting young star located in a cometary globule in the Gum Nebula. This radiation-driven structure is an unusual environment for observations of planet formation, and differs greatly from the low-mass star-forming regions disks are most commonly observed in. Aims. Aided by a collection of visual and spectroscopic data available for this system, our aim is to infer the possibility of embedded planets existing within the disk and how the system's environment may affect its disk morphology. Methods. Using data from the VLT's instruments XSHOOTER, ESPRESSO, and most prominently SPHERE, along with data from ALMA, we made a variety of measurements (geometric, photometric, and otherwise) to characterise the observed disk features and attributes such as spiral arms and eccentricity. Mapping of the velocity components was also undertaken using the ALMA gas line data to characterise disk orientation and determine the likelihood that the system is experiencing a late-stage infall event. Results. The disk is measured to have a position angle of 28.06 ± 0.02^° and an inclination of 42.5 ± 0.5^°. The disk is found to be eccentric with measured e ≍ 0.626 when deprojected. Under the assumption that the formation of a planet is wholly responsible for the primary and secondary spiral arms, we find the mass of such a planet can range between 0.004 and 3 Jupiter masses. Measurements of the velocities associated with nearby globule cloud material return reasonable velocities for a late-stage infall event. We estimate the far-ultraviolet (FUV) field strength at AT Pyx's location to be low in comparison to other surveyed disks. We also find that AT Pyx is possibly a binary system. Conclusions. AT Pyx is the first disk within a cometary globule to be spatially resolved, and is now the first such disk to be investigated to this extent. The work of this paper could potentially be a first step into the further study of disks in the moderate FUV environment of the Gum Nebula and its globules.

ALMA Band 1 observations of the ρ Oph W filament: I. Enhanced power from excess microwave emission at high spatial frequencies

First Author: Casassus, S.
Instruments: ALMA_Band_1
ProgramIDs: 2023.1.00265.S
BibCode: 2026A&A...707A.255C

Context. The ρ Oph W photo-dissociation region (PDR) is an example source of bright excess microwave emission (EME), over synchrotron, free-free, and the Rayleigh-Jeans tail of the sub-millimetre (sub-mm) dust continuum. Its filamentary morphology follows roughly that of the IR poly-cyclic aromatic hydrocarbon (PAHs) bands. The EME signal in ρ Oph W drops abruptly above ~30GHz and its spectrum can be interpreted in terms of electric-dipole radiation from spinning dust grains (or 'spinning dust'). Aims. Deep and high-fidelity imaging and spectroscopy of ρ Oph W may reveal the detailed morphology of the EME signal, free from imaging priors, while also enabling a search for fine structure in its spectrum. The same observations may constrain the spectral index of the high-frequency drop. Methods. An ALMA Band 1 mosaic yields a deep deconvolved image of the filament at 36-44 GHz, which we used as template for the extraction of a spectrum via cross-correlation in the uv plane. Simulations and cross-correlations on near-infrared ancillary data yield estimates of flux loss and biases. Results. The spectrum is a power law, with no detectable fine structure. It follows a spectral index α = −0.78 ± 0.05, in frequency, with some variations along the filament. Interestingly, the Band 1 power at high spatial frequencies increases relative to that of the IR signal, with a factor of two more power in Band 1 at ~20" than at ~100 " (relative to IRAC 3.6 μm). An extreme example of such radio-only structures is a compact EME source, without an IR counterpart. It is embedded in strong and filamentary Band 1 signal, while the IRAC maps are smooth in the same region. We provide multi-frequency intensity estimates for spectral modelling.

Observations of the temporal evolution of Saturn's stratosphere following the Great Storm of 2010─2011: II. Latitudinal distribution of CO and stratospheric winds

First Author: Cavalié, T.
Instruments: ALMA_Band_6
ProgramIDs: 2011.0.00808.S
BibCode: 2026A&A...707A.240C

Context. Saturn's Great Storm of 2010─2011 has produced two stratospheric hot spots, the "beacons," that eventually merged to produce a gigantic one in April and May 2011. This beacon perturbed stratospheric temperatures, hydrocarbon, and water abundances for several years. Aims. We aim to assess whether the beacon induced any perturbation in another oxygen species, namely CO. A second goal is to measure how the vortex perturbed the stratospheric wind regime. Methods. We conducted interferometric observations of Saturn in the submillimeter range with SMA and ALMA to spatially resolve the CO (J=3─2) and (J=2─1) emissions, respectively. We used a previously determined CO vertical profile as a template, to search for (i) the meridional distribution of CO and (ii) variations of the CO abundance associated with the storm. The high spatial and spectral resolutions of the ALMA observations enabled us to retrieve the winds from the Doppler shifts induced by the winds on the lines. Results. Despite limitations resulting from the removal of baseline ripples, we find a relatively constant meridional distribution of CO. The average CO mole fraction implied by the adopted and rescaled 220-year-old-comet-impact vertical profile is (1.7±0.7)×10⁻⁷ at 0.3 mbar, i.e., where the contribution functions peak. We also find that the CO abundance has not been noticeably altered in the beacon. The winds measured at 1 mbar show striking differences with those measured in 2018, after the demise of the beacon. We find the signature of the vortex as an anticyclonic feature. The equatorial prograde jet is 100─200 m s⁻¹ slower, and broader in latitude, than in quiescent conditions. We also detect several prograde jets in the southern hemisphere. Finally, we detect a retrograde jet at 74°N which could be a polar jet caused by the interaction of the Saturn magnetosphere with its atmosphere. Conclusions. With Saturn's equinox season approaching, new wind measurements would enable the findings presented in this paper to be confirmed by probing the two hemispheres equally and searching for a southern retrograde polar jet.

The Polarization and Magnetic Field of the Radio Arc as Observed by ALMA at 100 GHz

First Author: Salem, Nora
Instruments: ALMA_Band_3
ProgramIDs: 2024.1.00515.S
BibCode: 2026ApJ..1000..129S

The unique Galactic center nonthermal filaments (NTFs) have been a focus of investigations for over 40 yr. The most prominent manifestation of the NTFs is a bundle of parallel filaments known as the Radio Arc. Radio polarimetric observations made with the Very Large Array (VLA) at 10 GHz have revealed an alternating magnetic field pattern in the Radio Arc that could either be a result of multiple field systems being encountered along the line of sight or an intrinsic feature of the Radio Arc. These VLA observations were not able to distinguish between these possibilities due to the large rotation measures encountered toward the source. We present Atacama Large Millimeter/submillimeter Array (ALMA) 100 GHz observations of the Radio Arc that are not impacted by significant Faraday effects. The observations reported here represent both the first time that ALMA has been used to study the NTFs and the first time 100 GHz polarimetric observations have been conducted on the Radio Arc. We find a uniformly rotated magnetic field with respect to the NTF filament orientation, with the angle of rotation being constant along the length of each filament. However, we find a systematically different magnetic field orientation in different Radio Arc filaments. We use this field pattern to update our understanding of the line-of-sight structures local to the Radio Arc. We find that the magnetic field inferred from our ALMA observations is likely a result either of confusion from multiple magnetic field systems or because the polarization is centrally concentrated within the NTF filaments.

First Determination of the Cosmic Microwave Background Radiation Temperature at z = 0.68 Using Molecular Absorption Lines

First Author: Kotani, Tatsuya
Instruments: ALMA_Band_3, ALMA_Band_4
ProgramIDs: 2016.1.00031.S
BibCode: 2026ApJ..1000..141K

We analyzed millimeter-wave data toward the quasar B0218+357 observed with the Atacama Large Millimeter/submillimeter Array and obtained absorption spectra of the J = 2─1 and J = 3─2 rotational transitions of HCN, HCO⁺, HNC, H¹³CN, and H¹³CO⁺ at the cosmological redshift of z = 0.68. For HCN, HCO⁺, and HNC, we identified two distinct absorption components that are common to both transitions, whereas a single component was detected in the isotopologue spectra. In this paper, we accurately evaluate the excitation temperatures and their uncertainties from the absorption strengths of these components and use them to determine the cosmic microwave background radiation (CMB) temperature. Uncertainties in the continuum covering factor were propagated into the excitation temperature via Monte Carlo sampling. We further corrected the observed optical depths for biases due to column-density nonuniformity by assuming a lognormal column-density distribution. Under the assumption that the rotational levels are in radiative equilibrium with the CMB, we derived excitation temperature profiles in the optically thin regime. Because the excitation of HCO⁺ is biased by an additional velocity component and partial collisional excitation, this species was excluded from the final determination of the CMB temperature. From a weighted mean of the excitation temperatures obtained from HCN and HNC, we determined the CMB temperature at z = 0.68 to be 4.50 ± 0.17 K. This constitutes the first measurement of the CMB temperature at z = 0.68 based on a quasar absorption line system and represents the most precise determination at this redshift, highly consistent with the standard Big Bang cosmological model.

The GUAPOS project: VII. Physical structure and molecular environment of the G31.41+0.31 HII region

First Author: Cesaroni, R.
Instruments: ALMA_Band_3
ProgramIDs: 2017.1.00501.S
BibCode: 2026A&A...707A.327C

Context. Ionised regions around OB-type stars, formed at an early stage of their evolution, are important in the investigation of the formation processes of these objects. Thus far, however, only a few observations of their physical structure and interaction with the parental molecular cloud have been carried out. The high resolution and high sensitivity of new instruments such as ALMA and the upgraded VLA allow us to fill in this knowledge gap. Aims. We investigate the well-known core-halo ultracompact HII region G31.41+0.31 and the surrounding molecular clump to determine the density and temperature of both the ionised and neutral gas, and to possibly obtain a 3D picture of their spacial distribution. Methods. We took advantage of the full-band frequency coverage at 3 mm obtained with ALMA for the GUAPOS project to image the emission of a plethora of hydrogen recombination lines towards the G31.41+0.31 HII region, as well as several molecular transitions that serve as tracers of medium-density (~10⁴−10⁶ cm⁻³) gas. The line data are complemented by continuum measurements obtained with the VLA at 1 cm and 7 mm. By fitting these lines with a model that takes into account non-local thermal equilibrium (NLTE) effects, we were able to investigate the density and temperature structure and the velocity field of the region. Results. Our findings, based on a model fit accounting for NLTE effects, indicate that the electron temperature of the HII region mostly spans a range between 5000 and 6000 K, while the density varies between 2500 and 7500 cm⁻³. All in all, the distribution of these parameters, along with the corresponding velocity field hint at a cometary shaped HII region expanding away from the observer to the NW. The molecular gas appears to be still infalling towards the peak of the UC HII region, while its density and temperature are consistent with pressure confinement of the ionised gas to the SE.

Low Dust Mass and High Star Formation Efficiency at z > 12 from Deep ALMA Observations

First Author: Mitsuhashi, Ikki
Instruments: ALMA_Band_6, ALMA_Band_8
ProgramIDs: 2021.A.00020.S, 2023.A.00017.S, 2023.A.00037.S
BibCode: 2026ApJ..1000..159M

We investigate the dust mass buildup and star formation efficiency of two galaxies at z > 12—GHZ2 and GS-z14-0—by combining Atacama Large Millimeter/submillimeter Array and JWST observations with an analytical model that assumes dust at thermal equilibrium. We obtained 3σ constraints on the dust mass of logMdust/M⊙<5.0 and <5.3, respectively. These constraints are in tension with a high dust condensation efficiency in stellar ejecta but are consistent with models with a short metal accretion timescale at z > 12. Given the young stellar ages of these galaxies (t_age ∼ 10 Myr), dust grain growth via accretion may still be ineffective at this stage, though it likely works efficiently to produce significant dust in galaxies at z ∼ 7. The star formation efficiencies, defined as the star formation rate divided by the molecular gas mass, reach ∼10 Gyr⁻¹ over a 10 Myr timescale, aligning with the expected redshift evolution of "starburst" galaxies with efficiencies that are ∼0.5─1 dex higher than those in main-sequence galaxies. This starburst phase seems to be common in UV-bright galaxies at z > 12 and is likely associated with the unique conditions of the early phases of galaxy formation, such as bursty star formation. Direct observations of molecular gas tracers like [C II] will be crucial to further understanding the nature of bright galaxies at z > 12.

Active Galactic Nucleus Feedback and the Development of Dusty Multiphase Gas in X-Ray Emitting Elliptical Galaxies

First Author: Temi, Pasquale
Instruments: ALMA_Band_6
ProgramIDs: 2011.0.00735.S, 2015.1.00860.S
BibCode: 2026ApJ..1000..144T

This paper investigates the physical and kinematic properties of dust-rich regions in a small sample of group-centered elliptical galaxies, emphasizing their connection with the hot X-ray emitting gas and detailed dust grain characteristics. Comprehensive multiwavelength data—including Hα and CO emission detected by Multi Unit Spectroscopic Explorer and Atacama Large Millimeter/submillimeter Array—demonstrate the presence of dust clouds embedded within complex, hot X-ray atmospheres shaped by active galactic nucleus (AGN) feedback. X-ray images show bubbles and cavities surrounded by bright rims. We find that dust regions containing molecular gas traced by CO are preferentially located at the rims of these X-ray cavities, suggesting that AGN-driven outflows enhance the condensation of cold, dusty gas at these compressive interfaces. Kinematic measurements indicate that molecular and ionized gas phases are dynamically and spatially linked, supporting the framework of a multiphase medium arising from the top-down condensation rain in the hot plasma and related chaotic cold accretion. Crucially, spatial variations in the total-to-selective extinction ratio R_V show that regions where dust, CO, and Hα emission coincide exhibit notably smaller R_V values, implying steeper extinction curves and the predominance of smaller or less evolved dust grains within these mixed-phase environments. This contrasts with larger R_V values found elsewhere in the dust clouds, suggesting grain growth or survival mechanisms within shielded cold gas.

The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). XIII. Core Mass Function, Lifetime, and Growth of Prestellar Cores

First Author: Morii, Kaho
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00192.S, 2017.1.00716.S, 2015.1.01539.S
BibCode: 2026ApJ...997..155M

The core mass function (CMF) of prestellar cores is essential for understanding the initial conditions of star and cluster formation. However, the universality of the CMF and its relationship to the initial mass function (IMF) remain unclear. We study the CMF in the earliest stage of high-mass star formation using 461 prestellar core candidates and 254 protostellar cores as a part of the ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). We find that prestellar core candidates tend to have lower masses than protostellar cores. We also find that the lifetime of prestellar cores is several times longer than the freefall time, although it approaches the freefall time as the core mass increases. The CMF, including both protostellar and prestellar cores, has a power-law slope of −2.05 ± 0.04, shallower than Salpeter's IMF slope of −2.35. Conversely, the CMF of gravitationally bound, prestellar cores has a steeper slope (−2.32 ± 0.30), indistinguishable from Salpeter's slope. This finding is consistent with observations in both low-mass star-forming regions and high-mass protoclusters, implying a universal core formation mechanism. The protostellar CMF with a larger maximum core mass can be reproduced by the prestellar CMF when an external gas infall is considered. The inferred mass infall rate is higher than the Bondi─Hoyle─Lyttleton accretion rate and follows a shallower mass dependence (smaller power-law index), more consistent with the tidal-lobe accretion. This may contribute to the evolution of CMFs seen in later stages.

CH₃OH and HCN in Interstellar Comet 3I/ATLAS Mapped with the ALMA Atacama Compact Array: Distinct Outgassing Behaviors and a Remarkably High CH₃OH/HCN Production Rate Ratio

First Author: Roth, Nathan X.
Instruments: ALMA_Band_7
ProgramIDs: 2024.1.00137.T, 2024.1.00477.T, 2024.A.00049.S
BibCode: 2026ApJ...999L..32R

We report the detection of methanol (CH₃OH) toward interstellar comet 3I/ATLAS using the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array (ALMA) on UT 2025 August 28, September 18 and 22, and October 1 and of hydrogen cyanide (HCN) on September 12 and 15. These observations spanned pre-perihelion heliocentric distances (r_H) of 2.6─1.7 au. The molecules showed outgassing patterns distinct from one another, with HCN production being depleted in the sunward hemisphere of the coma, whereas CH₃OH was enhanced in that direction. Statistical analysis of molecular scale lengths in 3I/ATLAS indicated that CH₃OH included production from coma sources at L_p > 258 km at 99% confidence. However, low signal-to-noise ratio (S/N) on long baselines, which sample emission on small spatial scales closest to the nucleus, prevented definitively ruling out CH₃OH as purely a parent species. In contrast, HCN production was indistinguishable from direct nucleus sublimation. The CH₃OH production rate increased sharply from August through October, including an uptick near the inner edge of the H₂O sublimation zone at r_H = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH₃OH/HCN ratios in 3I/ATLAS of 124−34+30 and 79−14+11 on September 12 and 15, respectively, are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C/2016 R2 (Pan-STARRS).

exoALMA. XX. Tomographic Detection of Embedded Planets in Protoplanetary Disks

First Author: Izquierdo, Andrés F.
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ..1000L..13I

The exoALMA Large Program has revealed a wealth of substructures in the dust and molecular line emission of several protoplanetary discs, suggesting that planet formation may unfold within highly dynamic environments. Using synthetic observations of planet─disk interactions and disk instabilities, we demonstrate how the origin of these substructures can be investigated through a tomographic study of molecular lines, extending the scope of the analysis beyond line-centroid kinematics alone. Our results indicate that with only a few hours of ALMA integration at moderate angular resolution ( 0.″15−0.″30 ), it is possible to identify the key signatures driven by planets more massive than 0.1% of the stellar mass. These signatures manifest not only as deviations from Keplerian motion but also as localized line broadening, enabling accurate constraints on the orbital radius and azimuthal location of the planets. We further show that a diagnostic based on line skewness in spectrally resolved observations can help distinguish between planetary and instability-driven signatures, owing to the distinct degrees of velocity coherence associated with each mechanism. Finally, we apply this tomographic analysis to exoALMA CO line data for the disks of HD 135344B and MWC 758. In HD 135344B, we identify strongly localized velocity and line-width perturbations, suggesting the possibility of three massive planets embedded in the disk: one at R = 95 au, exterior to the continuum substructures, and two within dust gaps at R = 41 au and R = 73 au. For MWC 758, the dominance of vertical-velocity spirals over localized signatures is consistent with predictions from models of moderate disk eccentricities or warps, potentially induced by a substellar companion in the inner regions of the system.

exoALMA. XXIII. Estimating Disk and Planet Properties from Dust Morphologies with DBNets 2.0

First Author: Ruzza, Alessandro
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ..1000L..16R

The exoALMA large program provided an unprecedented view of the morphologies and kinematics of 15 circumstellar disks, offering a biased but homogenous and well-characterized sample for population-level analysis. Continuum observations revealed numerous dust substructures, known to be potential signatures of embedded planets. We analyze the observed dust morphologies with the simulation-based inference tool DBNets2.0, assuming these are due to embedded planets at fixed locations, to infer the system's properties. We estimate the putative planet mass, the disk α viscosity, scale height, and dust Stokes number that would reproduce 19 substructures in 13 of the 15 exoALMA disks. We compare our results with literature estimates derived with different methods, and find good agreement in most cases. We further explore the implications of the inferred disk properties for accretion, showing that for the Herbig stars in our sample, the implied viscous accretion timescales are too long to account for their observed stellar accretion rates. Regarding planet migration, our results favor inward migration, with only three putative planets expected to migrate outward. Finally, we check for correlations of the inferred disk and planet properties with the disks' gas-to-dust mass ratio, nonaxisymmetry index, and masses of the gas, dust, and host stars, finding no remarkable trends.

exoALMA XXII: A Two-dimensional Atlas of Deviations from Keplerian Disks

First Author: Fukagawa, Misato
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.01123.L
BibCode: 2026ApJ..1000L..15F

Protoplanetary disks are the birthplaces of planetary systems, and deviations from Keplerian rotation imprinted in disk gas kinematics serve as key tracers of physical processes and the presence of protoplanets within disks. Using the CO (J = 3─2) data from the exoALMA Large Program, encompassing 15 disks, we constructed two-dimensional (2D) maps of centroid velocity, line width, and peak intensity, and extracted non-Keplerian deviations by subtracting smooth Keplerian models. This Letter provides the first systematic and uniform overview of 2D gas substructures across the entire exoALMA sample. We find that all targets exhibit large-scale deviations from smooth Keplerian disks, displaying a variety of morphologies, including spiral-like structures, arc- or ring-like features, and patterns indicative of variations in the emitting surface height. Nonaxisymmetric spiral-arm features are detected or suggested in five disks (CQ Tau, MWC 758, HD 135344B, HD 34282, and SY Cha), and are preferentially found in Herbig Ae/Fe systems. In contrast, some other sources (J1852, PDS 66, and V4046 Sgr), despite exhibiting noticeable deviations, appear to be dynamically quieter. This 2D atlas suggests that kinematic substructures are ubiquitous in large (≳100 au) protoplanetary disks with ages of a few million years, based on the observations obtained with sufficient sensitivity at a moderate-to-high spatial resolution of ∼20 au and high-velocity resolution of ∼0.1 km s⁻¹.

ALMA Observations of Cold Methanol Gas in the Large Magellanic Cloud: N79 South Giant Molecular Cloud

First Author: Mondal, Suman Kumar
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2017.1.01323.S, 2018.1.01366.S, 2019.1.01770.S
BibCode: 2026ApJ...998..277M

We report Atacama Large Millimeter/submillimeter Array continuum and molecular line observations at 0.1 pc resolution toward the super star cluster (SSC) candidate H72.97−69.39 in the N79 region of the LMC. The continuum emission has a sharp peak around the SSC candidate but is also widely distributed. We identify two continuum sources at the northern (N79S-1) and northwestern (N79S-2) positions of the SSC continuum peak, associated with CH₃OH emission. In addition to CH₃OH, we also detect H₂CO, H₂CS, CS, SO, CO, CN, and CCH at the positions of N79S-1 and N79S-2. The rotation diagram analysis of CH₃OH and SO lines yields an average gas temperature of 13 ± 0.4 K for N79S-1 and 15 ± 0.9 K for N79S-2. Most emission lines exhibit line widths of less than 2.8 km s⁻¹, consistent with emissions from cold, dense molecular cloud cores. The abundance of cold CH₃OH gas is estimated to be (2.1 ± 1.1) × 10⁻⁹ at N79S-1 and (4.5 ± 2.5) × 10⁻¹⁰ at N79S-2. Despite the lower metallicity in the LMC, the CH₃OH abundance at N79S-1 is comparable to that of similar cold sources in our Galaxy. However, the formation of organic molecules is inhibited throughout the N79 regions, as can be seen in the nondetection of CH₃OH in most of the regions. The two positions N79S-1 and N79S-2 would be exceptional positions, where CH₃OH production is efficient. The possible origins of cold CH₃OH gas in these dense cores are discussed, along with a possible explanation for the nondetection of CH₃OH in the SSC candidate.

An observational study of rotation and binarity of Galactic O-type runaway stars

First Author: Carretero-Castrillo, M.
Instruments: FEROS
ProgramIDs: unknownID
BibCode: 2026A&A...705A.215C

Context.Gaia Data Release 3 (DR3) has revealed new massive runaway stars and large spectroscopic surveys have now enable detailed characterization studies. However, the relative contributions of binary supernova (BSS) and dynamical ejection (DES) scenarios to explain their runaway origin remain poorly constrained, particularly in the Milky Way. Aims. We aim to characterize the largest sample of Galactic O-type runaway stars ever investigated through their kinematics, rotation, and binarity with the ultimate objective of shedding light on their potential runaway origins. Methods. We used the GOSC-Gaia DR3 catalog of normal and runaway stars, along with IACOB spectroscopic information to build a sample with 214 O-type stars with information on the projected rotational velocities (v sin i). We also built a subsample of 168 O-type stars with additional information about their likely single (LS) or single-lined (SB1) spectroscopic binary nature. We also considered an additional sample of 65 double-lined (SB2) spectroscopic binaries. Results. We find that among our sample of Galactic O-type runaways, most (74%) have v sin i < 200 km s⁻¹, whereas for normal stars this fraction is slightly higher (82%). There are no fast-moving ( V PEC 2 D > 85 km s⁻¹) runaways that have been shown to be fast rotators (v sin i ≥ 200 km s⁻¹), except for HD 124 979. Runaways exhibit lower SB1 fractions than normal stars, with no runaway SB1 fast-rotating systems; on average, runaways rotate faster than normal stars; and their runaway fraction is higher among fast rotators (44%) versus the slow rotators (34%). This is consistent with BSS dominance for fast rotators. We also found that SB2 systems hardly reach runaway velocities with a low runaway fraction (10%). Runaways with V PEC 2 D > 60 km s⁻¹ are mostly single and interpreted as DES products, while runaways with V PEC 2 D > 85 km s⁻¹ are also interpreted as two-step products, with the binary V479 Sct/LS 5039 a likely example. Finally, we found that three of 12 runaway SB1 systems are high-mass X-ray binaries. Conclusions. Our observational study reveals that Galactic O-type runaways are dominated by slow rotators. The study points to a dominance of BSS among fast-rotating runaways and of DES and the two-step scenario among the high-velocity ones. The observed trends provide valuable constraints on models on the origins of runaway stars.

Observational evidence for a possible link between PAH emission and dust trap locations in protoplanetary disks

First Author: van der Marel, Nienke
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2012.1.00303.S, 2012.1.00631.S, 2013.1.00100.S, 2013.1.00157.S, 2013.1.00498.S, 2015.1.00773.S, 2015.1.00979.S, 2015.1.01600.S, 2016.1.00336.S, 2016.1.00340.S, 2016.1.00344.S, 2016.1.00484.L, 2016.1.00826.S, 2017.1.01424.S, 2018.1.00689.S, 2018.1.01458.S, 2021.1.00709.S, 2021.1.00854.S, 2021.1.01137.S, 2022.1.01302.S
BibCode: 2026A&A...706A.214V

Context. Polycyclic aromatic hydrocarbons (PAHs) are commonly detected in protoplanetary disks, but it is unclear what causes the wide range of intensities across the samples. Aims. For this work, the measured PAH intensities of a range of disks were compared with ALMA dust continuum images in order to test whether there is evidence that PAHs are frozen out on pebbles in dust traps and only sublimate under certain conditions. Methods. A sample was constructed from 26 T Tauri and Herbig disks located within 300 pc, with constraints on the 3.3 μm PAH intensity and with high-resolution ALMA continuum data. The midplane temperature was derived using a power law or via radiative transfer modeling. The warm dust mass was computed by integrating the flux within the 30 K radius and converted to a dust mass. Results. A strong correlation with a Pearson coefficient of 0.88±0.07 between the 3.3 μm PAH intensity and the warm dust mass was found. The correlation is driven by the combination of deep upper limits and strong detections corresponding to a range of warm dust masses. Possible correlations with other disk properties, for example a far-UV radiation field or total dust mass, are much weaker. Correlations with PAH features at 6.2, 8.6, and 11.3 μm are potentially weaker, but this could be explained by the smaller sample for which these data were available. Conclusions. The correlation is consistent with the hypothesis that PAHs are generally frozen out on pebbles in disks, and are only revealed in the gas phase if those pebbles have drifted toward warm dust traps inside the 30 K radius and vertically transported upward to the disk atmosphere with sufficiently high temperature to sublimate PAHs into the gas phase. This is similar to previous findings on complex organic molecules in protoplanetary disks, and provides further evidence that the chemical composition of the disk is governed by pebble transport.

Tracing Pebble Drift History in Two Protoplanetary Disks with CO Enhancement

First Author: Armitage, Tayt
Instruments: ALMA_Band_3, ALMA_Band_5, ALMA_Band_6
ProgramIDs: 2018.1.01055.L, 2021.1.00899.S
BibCode: 2026ApJ...998..308A

Pebble drift is an important mechanism for supplying the materials needed to build planets in the inner region of protoplanetary disks. Thus, constraining pebble drift's timescales and mass flux is essential to understanding planet formation history. Current pebble drift models suggest pebble fluxes can be constrained from the enhancement of gaseous volatile abundances when icy pebbles sublimate after drifting across key snowlines. In this work, we present Atacama Large Millimeter/submillimeter Array observations of spatially resolved ¹³C¹⁸O J = 2─1 line emission inside the midplane CO snowline of the HD 163296 and MWC 480 protoplanetary disks. We use radiative transfer and thermochemical models to constrain the spatial distribution of CO gas column density. We find that both disks display centrally peaked CO abundance enhancement of up to 10 times of the Interstellar Medium (ISM) abundance levels. For HD 163296 and MWC 480, the inferred enhancements require 250─350 and 480─660 M_⊕ of pebbles to have drifted across their CO snowlines, respectively. These ranges fall within cumulative pebble mass flux ranges to grow gas giants in the interior to the CO snowline. The centrally peaked CO enhancement is unexpected in current pebble drift models, which predict CO enhancement peaks at the CO snowline, or is uniform inside the snowline. We propose two hypotheses to explain the centrally peaked CO enhancement, including a large CO desorption distance and CO trapped in water ice. By testing both hypotheses with the 1D gas and dust evolution code chemcomp, we find that volatile trapping (about 30%) best reproduces the centrally peaked CO enhancement observed.

Testing the Physical Parameter Constraining Power of HCN and HNC with Neural Networks

First Author: Behrens, Erica
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_5, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2017.1.00161.L, 2018.1.00162.S
BibCode: 2026ApJ...998..274B

We quantify the utility of HCN and HNC to characterize gas conditions in the nearby starburst galaxy NGC 253. We use measurements from the Atacama Large Millimeter/Submillimeter Array (ALMA) Large Program ALCHEMI: the ALMA Comprehensive High-resolution Molecular Inventory. Using different subsets of the eight total HCN and HNC transitions measured by ALCHEMI, we test the number and combinations of transitions necessary for constraining the temperature, H₂ volume and column densities, cosmic-ray ionization rate, and beam-filling factor in three representative regions within NGC 253. We use these combinations of HCN and HNC transitions to constrain chemical and radiative transfer models, and infer the gas conditions using a Bayesian nested sampling algorithm combined with neural network models for increased efficiency. By comparing the shapes of the resulting posterior distributions, as well as the medians and uncertainties for each gas parameter, from each test case to what we obtain with the full set of eight transitions (the control), we quantify how well each test reproduces the control. We find that multiple transitions each of both molecules are required to obtain a median parameter value within a factor of 2 of the control with an uncertainty less than 2─3 times that of the control. We also find that transition combinations which feature a range of upper-state energies are most effective. We show that single transitions, such as HCN J = 1─0 or 3─2, are among the worst-performing combinations and result in parameter values up to an order of magnitude different than the control.

Unveiling the Chemical Complexity and C/O Ratio of the HD 163296 Protoplanetary Disk: Constraints from Multiline ALMA Observations of Organics, Nitriles, and Sulfur-bearing and Deuterated Molecules

First Author: Kashyap, Parashmoni
Instruments: ALMA_Band_4, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2018.1.00181.S, 2018.1.01055.L, 2021.1.00138.S
BibCode: 2026ApJS..282...47K

The physical and chemical conditions within a protoplanetary disk play a crucial role in determining its chemical composition, which is subsequently inherited by any forming planets. To probe these conditions, high-resolution molecular line observations, coupled with modeling, are essential. In this study, we investigate the chemistry of the nearby, massive, and relatively line-rich protoplanetary disk around HD 163296 using high-resolution observations from the Atacama Large Millimeter/submillimeter Array (ALMA) across Bands 3, 4, 6, and 7. We constrain the disk-averaged and radial distributions of column density and excitation temperature for the detected molecules using the new retrieval code DRive. The disk chemistry is modelled using the astrochemical code PEGASIS, with variations in the initial elemental C/O ratio. Our modelling, informed by molecular observations of HCO⁺, DCO⁺, HCN, DCN, CS, HC₃N, H₂CO, CH₃OH, HNCO, and NH₂CHO, allows us to place strong constraints on the C/O ratio, with a best-fit value of 1.1 that is broadly consistent with previous estimates. We present the highest-resolution DCO⁺ emission map of this disk to date, revealing triple-ringed chemical substructures that closely align with the dust continuum rings. Additionally, our results provide the first and most stringent upper limits on the column densities of NH₂CHO and HNCO in this protoplanetary disk, measured at <7 × 10¹¹ cm⁻² and <1 × 10¹¹ cm⁻², respectively. Our chemical models suggest that NH₂CHO and HNCO predominantly form on grain surfaces within the disk. However, physicochemical desorption mechanisms are inefficient at releasing these species into detectable gas-phase abundances, yet they remain promising targets for future ALMA observations.

A Protoplanet Candidate in the PDS 66 Disk Indicated by Silicon Sulfide Isotopologues

First Author: Yoshida, Tomohiro C.
Instruments: ALMA_Band_4, ALMA_Band_7
ProgramIDs: 2017.1.01687.S, 2023.1.00334.S, 2023.1.00525.S
BibCode: 2026ApJ...999L..22Y

Despite observational progress in planet formation, the stage in which planetesimals grow into planets remains poorly understood. During this phase, protoplanets may develop gaseous envelopes that are warmer than the surrounding disk gas, potentially providing observable signatures through molecules otherwise depleted in cold regions. In this Letter, we report the detection of the silicon sulfide isotopologues ²⁸SiS J = 16−15 and ³⁰SiS J = 18−17 in the protoplanetary disk around PDS 66 (MP Mus) at a significance of ∼5σ−6σ, using the Atacama Large Millimeter/submillimeter Array. These constitute the second and first detections of ²⁸SiS and ³⁰SiS in a protoplanetary disk, respectively. The emission appears as a compact source at r = 60 au in the southwestern region of the disk, unresolved with a ∼0.″5 beam, and shows a velocity consistent with Keplerian rotation, suggesting a protoplanetary origin. By modeling the line fluxes, we constrain the emitting radius to ∼0.5−4 au and estimate a SiS mass of 10²²─10²³ g, corresponding to at least ∼10% of the silicon contained in local dust grains. Because complete sublimation of a substantial fraction of dust grains by local processes is difficult to achieve, this result instead implies an accumulation of silicon from a larger region. We propose that a circumplanetary envelope surrounding a low-mass protoplanet, where pebble accretion and subsequent sublimation of grains may enhance gaseous silicon abundance with respect to observable dust grains around it, can account for the observed characteristics.

A Multiwavelength Study of Comet C/2022 E3 (ZTF): Complementary ALMA and JWST Investigations of Water and Methanol in Cometary Comae

First Author: Foster, K. D.
Instruments: ALMA_Band_6
ProgramIDs: 2022.1.00997.T
BibCode: 2026AJ....171..162F

Long-period comets, which are often considered to be representative of material in the protoplanetary disk that formed the solar system, are ideal to investigate the question of chemical inheritance in astronomy. Determining the chemistry of comets, both individually and as a population, has become of great importance in comparative studies against sources representative of evolutionary precursors to planetary systems. Contemporaneous observations of long-period comet C/2022 E3 (ZTF) were obtained with JWST and the Atacama Large Millimeter/submillimeter Array (ALMA) in early 2023 March. This work focuses on CH₃OH measurements from both ALMA and JWST, as well as H₂O measurements from JWST. Radiative transfer modeling of CH₃OH and H₂O was performed to investigate spatial variations in rotational temperature, column density, and production rates, as well as a comparison of derived values between the two telescopes. Most of the spatial distributions of the modeled values are centrally peaked, and the modeled values from JWST are all within the error bars of the average values from ALMA. C/2022 E3 (ZTF) also displays an enhancement in modeled rotational temperature in the antisunward direction that is shown to be statistically significant. Based on non-LTE radiative transfer modeling, the declining H₂O rotational temperatures as a function of nucleocentric distance observed by JWST can be explained primarily as a result of rotational line cooling. The values derived in this work are in general agreement with single-dish millimeter-wave observations.

Multiband ALMA Polarization Observations of BHB 07-11 Reveal Aligned Dust Grains in Complex Spiral Arm Structures

First Author: Fourkas, Austen
Instruments: ALMA_Band_3, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2013.1.00291.S, 2016.1.01186.S
BibCode: 2026ApJ...999....4F

Polarization-mode observations from the Atacama Large Millimeter/submillimeter Array (ALMA) are powerful tools for studying the dust grain populations in circumstellar disks. Many sources exhibit polarization signatures consistent with aligned dust grains, yet the physical origin of this alignment remains uncertain. One such source is BHB 07-11, a Class I protobinary object in the Pipe Nebula with complex spiral arm structures in its circumbinary disk. While magnetic fields are often invoked to explain grain alignment in the interstellar medium, the contrasting conditions in circumstellar disk environments demand further investigation into grain alignment mechanisms. To determine BHB 07-11's dominant polarization mechanism, we leverage ALMA polarization-mode dust continuum observations in Bands 3 (λ = 3.1 mm), 6 (λ = 1.3 mm), and 7 (λ = 0.87 mm), in combination with high-resolution dust continuum and spectral line observations in Band 6. Observed polarization vectors in each band are consistent with emission from aligned grains and follow the structure of the spiral arms as shown in the high-resolution observations. Given the relationship between the observed polarization vector orientation and the spiral arms, we find that the polarization morphology is most consistent with grains aligned through a relative velocity flow between gas and dust in the spiral arms, as envisioned in the recently developed badminton birdie-like alignment mechanism, rather than alignment with a magnetic field or other known alignment mechanisms.

CARTA—Cube Analysis and Rendering Tool for Astronomy: A Tool for Big Imaging Data

First Author: Wang, Kuo-Song
Instruments: ALMA_Band_6, ALMA_Band_7, ISAAC
ProgramIDs: 67.C-0595, 2011.0.00647.S, 2015.1.00425.S, 2015.1.01538.S, 2016.1.00484.L
BibCode: 2026PASP..138b4506W

Data generated by modern telescopes continues to grow rapidly as a result of these instruments' advanced capabilities, including wide-field imaging with high angular and spectral resolution. The resulting image cubes are often too large for end users to download and analyze on local desktop computers efficiently. Consequently, it is essential to provide visual analytics tools that can access these large data cubes remotely while enabling efficient and responsive local visualization. The Cube Analysis and Rendering Tool for Astronomy (CARTA; https://cartavis.org), presented in this paper, addresses this challenge. CARTA employs a client─server architecture: data processing is handled on the server side, while the client runs in the user's local web browser to render images and analysis results. This design minimizes data transfer, reduces latency, and enables seamless interaction with massive image cubes without the need for remote rendering. The paper outlines CARTA's implementation, including its architecture, deployment modes, interfaces, and codebase. It also provides an overview of its core features and analytics tools for different types of astronomical data. A long-term development plan for advanced features is also discussed.

oMEGACat. VIII. A Subpopulation Census of ω Centauri

First Author: Clontz, C.
Instruments: MUSE
ProgramIDs: 099.D-0019, 098.D-0148, 097.D-0295, 096.D-0175, 095.D-0629, 094.D-0142, 109.23DV, 105.20CR, 0104.D-0257, 0103.D-0204, 0102.D-0270, 0101.D-0268, 0100.D-0161, 105.20CG
BibCode: 2026ApJ...998..177C

An understanding of the assembly history of the complex star cluster Omega Centauri has long been sought after, with many studies separating the stars on the color─magnitude diagram into multiple groupings across small magnitude ranges. Utilizing the oMEGACat combined astro-photometric and spectroscopic data set, we parse 14 subpopulations from the upper red giant branch to below the main-sequence turnoff. We combine our results with previous works to estimate the age and age spread of each population. We find that the chemically enhanced (P2) populations are all ∼1 Gyr younger (∼11.6 Gyr old) and have significantly higher intrinsic age spreads (0.6 Gyr) than the primordial (P1) populations (∼12.6 Gyr old, 0.3 Gyr spread), with the intermediate (Im) populations falling in between the two. Additionally, we connect for the first time the chromosome diagram to the two-stream age─metallicity relation, allowing us to link the P1 and P2 stars to the distinct star formation tracks, proposed to be in situ and ex situ contributions to the cluster's assembly. Our results are consistent with some suggested formation models and rule out others, but no current model can explain all observed features of the subpopulations.

Possible collision-induced outflows and triggered star formation in the molecular complex G34

First Author: Sun, Mingke
Instruments: LABOCA
ProgramIDs: 085.F-9526, 085.F-9505, 082.F-9701, 080.F-9701, 081.C-9501, 079.C-9501, 078.F-9040, 181.C-0885
BibCode: 2026MNRAS.546f2285S

G34 is an active star-forming region with complex velocity components. Within the 38─63 km s

$^{-1}$

velocity range, we identify a possible cloud─cloud collision at a distance of

$\sim$

3 kpc. Using the

$\rm ^{12}CO$

(

${\it J}$

= 1─0) line from the Purple Mountain Observatory 13.7-m millimeter telescope to trace the diffuse gas structures associated with the collision. The gas components at 38─50 and 53─63 km s

$^{-1}$

exhibit a U-shaped complementary distribution and a bridge feature in the position─velocity diagram. At the collision interface, the velocity dispersion of

$\rm ^{12}CO$

is significantly enhanced, which may result from the impact of the collision. We analyse the spatial distributions of 6.7 GHz CH

$_3$

OH masers, APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) clumps, H II regions, young stellar objects, and O-type stars, finding that most are concentrated near the collision interface. This supports a strong coupling between cloud─cloud collisions and star formation. In addition, we detect H I self-absorption features and molecular outflows at the interface. Based on observations of 6 and 2 cm H

$_2$

CO lines from the Effelsberg 100 m and Tianma Radio Telescope 64 m telescopes, along with NH

$_3$

lines from the Nanshan 26 m telescope, we derive an H

$_2$

volume density of

$10^4$

─

$10^5$

$^{-3}$

in the compressed region. Finally, we compare the collision time-scales (

$\gtrsim$

0.35 Myr), the dynamical age of the H II region G34.26+0.15 (

$\gtrsim$

0.33 Myr), and the outflow time-scale (

$\sim$

7.5 Myr). The results suggest that gas at the base of the U-shaped structure was compressed during the collision and driven into the outflow. After millions of years of evolution, the gas density increased, potentially triggering star formation.

Red Noise─based False Alarm Thresholds for Astrophysical Periodograms via Whittle's Approximation to the Likelihood

First Author: Ejaz, Amna
Instruments: HARPS
ProgramIDs: 074.D-0380, 086.C-0230
BibCode: 2026AJ....171..124E

Astronomers who search for periodic signals using Lomb─Scargle periodograms rely on false alarm level (FAL) estimates to identify statistically significant peaks. Although FALs are often calculated from white noise models, many astronomical time series suffer from red noise. Prewhitening is a statistical technique in which a continuum model is subtracted from the log power spectrum estimate, after which the observer can proceed with a white-noise treatment. Here we present a prewhitening-based method of calculating frequency-dependent FALs. We fit power laws and autoregressive models of order 1 to each Lomb─Scargle periodogram by minimizing the Whittle approximation to the negative log-likelihood (NLL), then calculate FALs based on the best-fit model power spectrum. Our technique is a novel extension of the Whittle NLL to datasets with uneven time sampling. We demonstrate FAL calculations using observations of α Cen B, GJ 581, HD 192310, synthetic data from the radial velocity (RV) fitting challenge, and Kepler observations of a differential rotator. The Kepler data analysis shows that only true rotation signals are detected by red noise FALs, while white noise FALs suggest all spurious peaks in the low-frequency range are significant. A high-frequency sinusoid injected into α Cen B logR'HK observations exceeds the 1% red noise FAL despite having only 8.9% of the power of the dominant rotation signal. In a periodogram of HD 192310 RVs, peaks associated with differential rotation and planets are detected against the 5% red noise FAL without iterative model fitting or subtraction. The software for calculating red noise─based FALs is available on GitHub.

Accretion History of AGNs: A Multiwavelength Comparison of X-Ray- and Infrared-selected AGNs

First Author: Kelly, Thresa
Instruments: VIRCAM
ProgramIDs: 179.A-2005
BibCode: 2026ApJ...997..366K

Identifying active galactic nuclei (AGNs) using only one wavelength region may miss AGNs with characteristics unfavorable for the identification method, which introduces bias in the sample. To better understand these selection effects, we compare the multiwavelength properties of 2584 X-ray- and IR-selected AGNs at z < 3 in the COSMOS field. The X-ray-selected sample consists of the 2219 AGNs with intrinsic 0.5─10 keV X-ray luminosity greater than 10⁴³ erg s⁻¹; the 993 IR-selected AGNs are identified by their high-contrast, power-law IR colors using Spitzer/IRAC observations. We find that both selection methods miss a significant fraction of AGNs, as only 24.3% of AGNs (628 out of the total of 2584 AGNs) are recovered by both selection criteria. X-ray selection can capture the most diverse range of multiwavelength spectral emission features, while IRAC selection is biased against AGNs with a steeply decreasing power flux (λF_λ) between 1 and 6 μm. For AGNs with X-ray detections, IRAC-selected sources are 2.5× more X-ray luminous than AGNs not identified by their IR colors. IRAC-selected AGNs without detectable X-rays are obscured, as they have a mean X-ray correction factor log(LX,obs/LX,int)= −1.4; 28.5%─42.2% of these AGNs are Compton-thick (according to estimated column densities). Only 1.4% of X-ray-selected AGNs are Compton-thick. The AGN selection technique used significantly impacts the overall characteristics of the resulting AGN sample.

ELFO: A Python Package for Emission Line Fitting Optimization in Integral Field Spectroscopy Data

First Author: Guo, Hui
Instruments: MUSE
ProgramIDs: 0103.B-0762
BibCode: 2026AJ....171..106G

Integral field spectroscopy (IFS) provides spatially resolved spectra, enabling detailed studies that address the physical and kinematic properties of the interstellar medium. A critical step in analyzing IFS data is the decomposition of emission lines, where different velocity components are often modeled with Gaussian profiles. However, conventional fitting methods that treat each spectrum independently often yield spatial discontinuities in the fitting results. Here, we present Emission Line Fitting Optimization (ELFO), a Python package for IFS spectral fitting. ELFO uses the results of neighboring spectra to determine multiple initial guesses and selects the result that exhibits spatial smoothness. We tested ELFO on IFS data of two quasars obtained from the Multi-Unit Spectroscopic Explorer, where it successfully corrected anomalous fits, revealed previously unresolved substructures, and made large-scale kinematic structures more evident. With minor modifications, this method can also be easily adapted to other IFS data and different emission lines.

Chemical analysis of the Milky Way's nuclear star cluster: Evidence for a metallicity gradient

First Author: Schultheis, M.
Instruments: KMOS
ProgramIDs: 60.A-9450, 093.B-0368
BibCode: 2026A&A...705A.235S

Context. The Milky Way nuclear star cluster (MWNSC) is located in the Galactic centre, together with the Milky Way nuclear stellar disc (MWNSD), and they dominate the gravitational potential within the inner 300 pc. However, the formation and evolution of the two systems and their possible connections are still under debate. Aims. We reanalysed the low-resolution KMOS spectra in the MWNSC with the aim of improving the stellar parameters (T_eff, log g, and [M/H]) for the MWNSC. Methods. We used an improved line list, especially dedicated for cool M giants, that allowed us to improve the stellar parameters and to obtain in addition global α-elements. A comparison with high-resolution IR spectra (from IGRINS) gives very satisfactory results and constrains the uncertainties to T_eff ≃ 150 K, log g ≃ 0.4 dex, and [M/H] ≃ 0.2 dex. Our α-elements agree within 0.1 dex compared to the IGRINS spectra. Results. We obtained a high-quality sample of 1140 M giant stars where we see an important contribution of a metal-poor population (∼20%) centred at [M/H] ≃−0.7 dex, while the most dominant part comes from the metal-rich population with [M/H] ≃ 0.26 dex. We constructed a metallicity map and find a metallicity gradient of ∼−0.1 ± 0.02 dex/pc favouring the inside-out formation scenario for the MWNSC.

Characterising the post-red supergiant binary system AFGL 4106 and its complex nebula with SPHERE/VLT

First Author: Tomassini, G.
Instruments: SPHERE
ProgramIDs: 0102.D-0501, 1104.C-0416
BibCode: 2026A&A...706A...5T

Context. Mass loss in evolved massive stars plays a critical role in shaping their circumstellar environments and enriching the interstellar medium. In binary systems, stellar interactions can further complicate this process, affecting stellar evolution, stellar yields, and nebular morphology. Aims. We aim to characterise the physical and morphological properties of the binary system AFGL 4106, which is composed of two evolved massive stars. Understanding its mass-loss processes and circumstellar environment offers insight into the late stages of stellar evolution in massive binary systems. Methods. We obtained high-angular-resolution, high-contrast imaging using VLT/SPHERE with ZIMPOL (optical) and IRDIS (near-infrared) across multiple filters. We used aperture photometry to extract the spectral energy distributions (SEDs) of each star and applied radiative-transfer modelling to study the system and its surrounding dusty environment. Results. The observations resolve both components of the binary and unveil a complex, dusty nebula featuring asymmetric structures and cavities. SED fitting yields stellar temperatures of T₁ = 6723 ± 196 K and T₂ = 3394 ± 264 K, along with bolometric luminosities of L₁ = (7.9 ± 0.18)×10⁴ L_⊙ and L₂ = (3.8 ± 0.11)×10⁴ L_⊙. These values support the classification of the primary as being in a post-red-supergiant (post-RSG) phase and the secondary as an active red supergiant (RSG). The luminosity ratio, combined with the inferred radii, indicates that both stars are at close yet distinct stages of their evolution. The binary is surrounded by an extended shell whose asymmetric morphology and large-scale features suggest interaction with the stellar winds and interstellar medium (ISM), and possibly the presence of a third, undetected companion. Conclusions. These observations provide the first resolved view of AFGL 4106's system and its dusty envelope. Our analysis sets constraints on the physical properties and evolutionary status of the system. This work contributes to our understanding of mass-loss processes in massive binaries and the shaping of nebulae around evolved stars.

Unveiling the white dwarf in the eclipsing polar HU Aquarii

First Author: Schwope, A. D.
Instruments: ULTRACAM_VLT
ProgramIDs: 075.D-0349, 075.D-0135, 075.D-0738
BibCode: 2026A&A...706A..41S

We present an analysis of high-speed u- and r-band photometry of the eclipsing polar HU Aqr that was obtained with ULTRACAM mounted on the VLT. The observations were performed during a low state, permitting us for the first time to determine the contact points of the white dwarf. Using LCURVE we could determine its size, and hence mass, with a direct method and with unprecedented accuracy. We determined the mass of the white dwarf as 0.78 ± 0.02 M_⊙, the mass ratio Q = M_WD/M_sec = 4.59, and the orbital inclination i = 87.° 4 ± 0.° 9. An extended warm region with a central temperature of ∼33 000 K was observed in the u-band at the location of the previous high-state accretion spot. Weak accretion was ongoing in the low state that led to cyclotron emission that could best be studied with the r-band data. It has a diameter of only 3° to 4° and is located much closer to the binary meridian than the accretion-heated region studied in the u-band. The longitudinal shift of the two accretion regions is of order 30°, due to early and late coupling of accreted matter onto the magnetic field lines in low and high accretion states, respectively. The low-state cyclotron-emitting region has a vertical extent of 0.005 − 0.016 R_WD, a value that seems to be correlated to the instantaneous accretion rate.

Unveiling the 3D structure of the central molecular zone from stellar kinematics and photometry: The 50 and 20 km/s clouds

First Author: Nogueras-Lara, Francisco
Instruments: HAWKI, VIRCAM
ProgramIDs: 195.B-0283, 198.B-2004, 179.B-2002
BibCode: 2026A&A...706A..18N

Context. The central molecular zone (CMZ), surrounding the Galactic centre, is the largest reservoir of dense molecular gas in the Galaxy. Despite its relative proximity, the 3D structure of the CMZ remains poorly constrained, primarily due to projection effects. Aims. We aim to constrain the line-of-sight location of two molecular clouds in the CMZ - the 50 and 20 km/s clouds - and to investigate their possible physical connection using stellar kinematics and photometry. This study serves as a pilot for future applications across the full CMZ. Methods. We estimated the line-of-sight position of the clouds by analysing stellar kinematics, stellar densities, and stellar populations towards the cloud regions and a control field. Results. We find an absence of westward moving stars in the cloud regions, which indicates that they lie on the near side of the CMZ. This interpretation is supported by the stellar density distributions. The similar behaviour observed in the two clouds, as well as in the region between them (the ridge), suggests that they are located at comparable distances and are physically linked. We also identified an intermediate-age stellar population (2-7 Gyr) in both regions, consistent with that observed on the near side of the CMZ. We estimated the line-of-sight distances at which the clouds and the ridge become kinematically detectable (i.e. where the proper motion component parallel to the Galactic plane differs from that of the control field at the 3σ level) by converting their measured proper motions parallel to the Galactic plane using a theoretical model of the stellar distribution. We find that the 50 and 20 km/s clouds are located at 43 ± 8 pc and 56 ± 11 pc from Sgr A^*, respectively, and that the ridge lies at 56 ± 11 pc; this supports the idea that the clouds are physically connected through the ridge.

Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): V721 CrA and BN CrA have wide and structured disks in the polarised infrared

First Author: Columba, G.
Instruments: ALMA_Band_6, SPHERE
ProgramIDs: 1104.C-0415, 2015.1.01301.S
BibCode: 2026A&A...706A..16C

Context. The environment within which stars form and evolve can play a crucial role in shaping their surrounding protoplanetary disks. This is the reason why homogeneous analyses of protoplanetary disks around young stars in the same star-forming region has become of great relevance in recent years. Aims. We present near-infrared scattered-light observations of the disks around two stars of the Corona Australis star-forming region, V721 CrA and BN CrA, obtained with VLT/SPHERE in the H band, as part of the DESTINYS large programme. Our objective is to analyse the morphology of these disks and highlight their main properties. Methods. We adopted an analytical axisymmetric disk model to fit the observations and performed a regression on key disk parameters, namely the dust mass, the height profile, and the inclination. We used RADMC-3D code to produce synthetic observations of the analytical models, with full polarised scattering treatment. Results. Both stars show resolved and extended disks with substructures in the near-IR. The disk of V721 CrA is vertically thicker, radially smaller (∼120 au), and brighter than that of BN CrA (∼190 au). It also shows spiral arms in the inner regions. The disk of BN CrA shows a dark circular lane, which could be either an intrinsic dust gap or a self-cast shadow, and a brightness enhancement along the disk minor axis. Both disks are compatible with the evolutionary stage of their parent subgroup within the CrA region: V721 CrA belongs to the on-cloud part of CrA, which is dustier, denser, and younger, whereas BN CrA is found on the outskirts of the older off-cloud group.

Constraining Nuclear Molecular Gas Content with High-resolution CO Imaging of GOALS Galaxies

First Author: Agostino, James
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2017.1.01235.S, 2018.1.01123.S, 2019.1.00811.S
BibCode: 2026ApJ...998..343A

We present measurements of the cool molecular gas mass around the nuclei of two gas-rich mergers, III Zw 035 and IRAS F01364−1042, whose enclosed masses (M_enc) within the central 40─80 pc would be overmassive if attributed entirely to the supermassive black hole (SMBH) mass and compared to SMBH─galaxy scaling relations. Our gas mass measurements are derived from Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 long-baseline observations of CO(J = 2─1) and 230 GHz continuum emission at 14─20 pc resolution, which probes below the resolving limit of the previous black hole mass measurements. Subtracting molecular gas mass from these enclosed masses is not enough to reconcile with black hole─galaxy relationships, but independently measuring M_enc using the cold CO(2─1) gas does shift the black holes down to their expected values. Still, these ALMA data reveal respective molecular gas masses of ∼3 × 10⁷ to ∼6 × 10⁸ M_⊙ within 70 pc of these black holes, which could challenge some black hole accretion models that assume nuclear gas like this has no angular momentum.

A surprisingly large asymmetric ejection from Mira A

First Author: Khouri, T.
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00191.S, 2018.1.00749.S, 2022.1.01071.S
BibCode: 2026A&A...707A.162K

Context. Stars with masses between roughly 1 and 8 M_⊙ end their lives on the asymptotic giant branch (AGB), when intense mass loss takes place, with major consequences for the chemical evolution of the universe. The mechanism responsible for the outflows is generally accepted to be radiation pressure acting on dust grains that form in the dense extended atmospheres of AGB stars. Dust formation is enabled, or at least dramatically enhanced, by the action of convection and stellar pulsations. The complex physics underlying convection, stellar pulsations, and dust nucleation precludes predicting AGB mass loss from first principles. Aims. Our aim was to characterize the recent mass ejections of the AGB star Mira A using observations of the inner envelope. In particular, we studied two lobes observed to be expanding away from Mira A to obtain empirical insights into the mass-ejection process. Methods. We investigated the evolution of the lobes using images of polarized light obtained at six epochs using the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) on the Very Large Telescope and of molecular emission at two epochs obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). Six lines of SO₂ were used to investigate the excitation temperature and column density of SO₂ in the lobes. We used the ¹³CO J = 3-2 line and radiative transfer models to constrain the column density of the gas, which allowed us to infer the abundances of SO, SO₂, AlO, AlF, and PO in the lobes. Results. While dust seems confined almost exclusively to the edges of the lobes, gas fills the lobes and displays higher densities than expected at the observed radial distances based on the large-scale mass-loss rate of Mira A, with a total gas mass in the lobes of ∼2 × 10⁻⁵ M_⊙. We find the expansion of the lobes to be consistent with both a constant velocity (ejection time in 2010 or 2011) or a decelerating expansion (ejection time in 2012). If ejection events with a similar magnitude happen periodically, we derive periods between 50 and 200 years to account for the mass-loss rate of Mira A. This periodicity is very uncertain because of the complexity of the circumstellar environment that hampers accurate determinations of the mass-loss rate. We find abundances in the lobes of ∼1.5 × 10⁻⁶ and ∼2.5 × 10⁻⁶ for SO and SO₂, respectively, when accounting for radiative transfer effects and of 2 × 10⁻¹⁰, 6.5 × 10⁻¹⁰, and 4 × 10⁻⁷ for AlO, AlF, and PO assuming LTE and optically thin emission. The strong variation in brightness of the different features identified in the polarized-light images is puzzling. We suggest that an asymmetric stellar radiation field preferentially illuminates specific regions of the circumstellar envelope at a given time, producing a lighthouse-like effect.

Spatially Resolved, Multiphase Mass Outflows of the Seyfert 1 Galaxy NGC 3227

First Author: Falcone, Julia
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.00254.S
BibCode: 2026ApJ...997...68F

We present spatially resolved mass outflow rates of the ionized and molecular gas in the narrow-line region of the Seyfert 1 galaxy NGC 3227. Using long-slit spectroscopy and [O III] imaging from from the Hubble Space Telescope's Space Telescope Imaging Spectrograph and Apache Point Observatory's Kitt Peak Ohio State Multi-Object Spectrograph, in conjunction with Cloudy photoionization models and emission-line diagnostics, we find a peak ionized mass outflow rate of Ṁion= 19.9 ± 9.2 M_⊙ yr⁻¹ at a distance of 47 ± 6 pc from the supermassive black hole (SMBH). Using archival data from the Gemini-North Near-infrared Field Spectrograph measuring H₂ 2.1218 μm emission, we find a maximum peak warm molecular outflow rate of ṀH2≤9×10−4 M_⊙ yr⁻¹ at a distance of 36 ± 6 pc from the SMBH. Using archival data from the Atacama Large Millimeter/submillimeter Array measuring CO(2─1) emission, we find a maximum peak cold molecular gas mass outflow rate of ṀCO≤ 23.1 M_⊙ yr⁻¹ at a distance of 57 ± 6 pc from the SMBH. For the first time, we calculate spatially resolved gas evacuation timescales for the cold molecular gas reservoirs ostensibly sourcing the outflows, and find that gas evacuating to ∼400 pc from the SMBH occurs on timescales of 10^6.0─10^7.6 yr. These results indicate that the multiphase active galactic nucleus (AGN) outflows are effective in clearing the inner few hundred parsecs of NGC 3227's gas content on timescales that may set the AGN duty cycle of 10⁵─10⁸ yr.

The Atacama Cosmology Telescope: Observations of supermassive black hole binary candidates: Strong sinusoidal variations at 95, 147, and 225 GHz in PKS 2131─021 and PKS J0805─0111

First Author: Hincks, Adam D.
Instruments: ALMA_Band_3, ALMA_Band_7
ProgramIDs: 2011.0.00001.CAL
BibCode: 2026A&A...706A.206H

Large sinusoidal variations in the radio light curves of the blazars PKS J0805─0111 and PKS 2131─021 have recently been discovered with an 18-year monitoring programme at the Owens Valley Radio Observatory, making these systems strong supermassive black hole binary (SMBHB) candidates. The sinusoidal variations in PKS 2131─021 dominate its light curves from 2.7 GHz to optical frequencies. We report sinusoidal variations observed in both objects with the Atacama Cosmology Telescope (ACT) at 95, 147, and 225 GHz consistent with the radio light curves. The ACT 95 GHz light curve of PKS 2131─021 agrees well with the contemporaneous 91.5 GHz ALMA light curve and is comparable in quality, while the ACT light curves of PKS J0805─0111, for which there are no ALMA or other millimetre light curves, show that PKS 2131─021 is not an isolated case, and that this class of AGN exhibits the following properties: (a) the sinusoidal pattern dominates over a broad range of frequencies; (b) the amplitude of the sine wave compared to its mean value is monochromatic (i.e. nearly constant across frequencies); (c) the phase of the sinusoid phase changes monotonically as a function of frequency; (d) the sinusoidal variations are intermittent. We describe a physical model for SMBHB systems, the modified Kinetic Orbital model, that explains all four of these phenomena. The monitoring of ∼8000 blazars by the Simons Observatory over the next decade should provide a large number of SMBHB candidates that will shed light on the nature of the nanohertz gravitational-wave background.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): VIII. A dust arc and non-Keplerian gas kinematics in HD 121617

First Author: Marino, S.
Instruments: ALMA_Band_7, SPHERE
ProgramIDs: 0101.C-0420, 2022.1.00338.L
BibCode: 2026A&A...705A.202M

Context. ExoKuiper belts around young A-type stars often host CO gas, whose origin is still unclear. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) includes six of these gas-bearing belts, to characterise their dust and gas distributions and investigate the gas origin. Aims. As part of ARKS, we observed the gas-rich system HD 121617 with a 0_⋅^'' 12 (14 au) resolution and discovered an arc of enhanced dust density. In this paper, we analyse in detail the dust and gas distributions and the gas kinematics of this system. Methods. We extracted radial and azimuthal profiles of the dust (in the millimetre and near-infrared) and gas emission (¹²CO and ¹³CO) from reconstructed images. To constrain the morphology of the arc, we fitted an asymmetric model to the dust emission. To characterise the gas kinematics, we fitted a Keplerian model to the velocity map and extracted the gas azimuthal velocity profile by deprojecting the data. Results. We find that the dust arc is narrow (1─5 au wide at a radius of 75 au), azimuthally extended with a full width at half maximum of ~90°, and asymmetric; the emission is more azimuthally compact in the direction of the system's rotation, and represents 13% of the total dust mass (0.2 M_⊕). From analysis of the scattered light and CO images, we conclude that the arc is much less pronounced or absent for small grains and gas. Finally, we find strong non-Keplerian azimuthal velocities at the inner and outer wings of the ring, as was expected due to strong pressure gradients. Conclusions. The dust arc resembles the asymmetries found in protoplanetary discs, often interpreted as the result of dust trapping in vortices. If the gas disc mass is high enough (≳20 M_⊕, requiring a primordial gas origin), both the radial confinement of the ring and the azimuthal arc may result from dust grains responding to gas drag. Alternatively, it could result from planet-disc interactions via mean motion resonances. Further studies should test these hypotheses and may provide a dynamical gas mass estimate in this CO-rich exoKuiper belt.

Sunyaev─Zeldovich detection of hot intracluster gas at redshift 4.3

First Author: Zhou, Dazhi
Instruments: ALMA_Band_3
ProgramIDs: 2015.1.01543.T, 2017.1.00273.S, 2022.1.00495.S, 2023.1.00124.S
BibCode: 2026Natur.649.1130Z

Most baryons in present-day galaxy clusters exist as hot gas (≳10⁷ K), forming the intracluster medium (ICM)¹. Cosmological simulations predict that the mass and temperature of the ICM decline towards earlier times, as intracluster gas in younger clusters is still assembling and being heated^{2, 3─4}. To date, hot ICM has been securely detected only in a few systems at or above z ≍ 2, leaving the timing and mechanism of ICM assembly uncertain^{5, 6─7}. Here we report the direct observation of hot intracluster gas via its thermal Sunyaev─Zeldovich signature in the protocluster SPT2349─56 with the Atacama Large Millimeter/submillimeter Array. SPT2349─56 hosts a large molecular gas reservoir and three radio-loud active galactic nuclei (AGN) within an approximately 100-kpc region at z = 4.3 (refs. ^{8, 9, 10─11}). The measurement implies a thermal energy of about 10⁶¹ erg in the core, about 10 times more than gravity alone should produce. Contrary to current theoretical expectations^3,4,12, the hot ICM in SPT2349─56 demonstrates that substantial heating can occur very early in cluster assembly, depositing enough energy to overheat the nascent ICM well before mature clusters become common at z ≍ 2.

The circumbinary disk of HD34700A: I. CO gas kinematics indicate spirals, infall, and vortex motions

First Author: Stadler, J.
Instruments: ALMA_Band_6
ProgramIDs: 2022.1.00760.S
BibCode: 2026A&A...707A.160S

Aims. We present the first high-resolution (∼0″.14) Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 dust continuum, ¹²CO J = 2-1, ¹³CO J = 2-1, and C¹⁸O J = 2-1 molecular line emission observations of the quadruple system HD 34700. In particular, HD34700AaAb is a spectroscopic binary (M_bin = 4 M_⊙) surrounded by two low-mass companions (B = 0.6 M_⊙, C = 0.4 M_⊙) at large separations. Its circumbinary disk is highly substructured, featuring numerous spiral arms and a large cavity observed in infrared (IR) scattered light. We aim to shed light on the nature of these features by examining the gas kinematics at work in the circumbinary disk. Methods. We analyzed the CO line channel and intensity moment maps. By fitting a Keplerian model to the line channel emission, we identified the residual motions and conducted a line spectra analysis. Results. We resolved an asymmetric continuum crescent on top of a dust ring at 0739 (138 au) colocated with the IR ring. The CO molecule's line emission traces a smaller cavity in gas, whose edge aligns with the inner rim of the ring detected in Hα emission at 0″.20 (65 au). The ¹²CO line emission and kinematics trace highly non-Keplerian motions (∼0.1∆υ_k) and these CO spiral features align well with the spiral structures in scattered light. The ¹²CO line spectra analysis reveals a streamer above the southeastern disk plane, likely falling onto the disk. The ¹³CO and C¹⁸O kinematics largely follow the disk's underlying Keplerian rotation, while ¹³CO exhibits tentative signs of anticyclonic vortex flows at the continuum crescent location. Conclusions. Our multimolecular line study suggests that the circumbinary disk of HD 34700A is highly perturbed in its upper layers, possibly warped and influenced by infalling material. While late-stage infall may account for the IR spirals and the formation of the vortex through Rossby wave instability, an embedded massive companion within the cavity might also be contributing to these features.

Magnetic threads and gravity: ALMA observations of the infrared dark cloud G14.225-0.506

First Author: Añez-López, Nacho
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00793.S
BibCode: 2026A&A...707A.165A

Context. In the star formation process, the interplay between gravity, turbulence, and magnetic fields is significant, with magnetic fields apparently serving a regulatory function by opposing gravitational collapse. Nonetheless, the extent to which magnetic fields are decisive relative to turbulence and gravity, as well as the specific environments and conditions involved, remains uncertain. Aims. This study aims to ascertain the role of magnetic fields in the fragmentation of molecular clouds into clumps down to core scales. Methods. We examined the magnetic field as observed with ALMA at core scales (approximately 10 000 AU/0.05 pc) toward the infrared dark cloud (IRDC) G14.225-0.506, focusing on three regions with shared physical conditions. We juxtaposed these data with prior observations at the hub-filament system scale (approximately 0.1 pc). Results. Our findings indicate a similar magnetic field strength and fragmentation level between the two hubs. However, distinct magnetic field morphologies have been identified across the three regions where the polarized emission is detected. In region N (i.e., the northern Hub: Hub-N), the large-scale magnetic field, perpendicular to the filamentary structure, persists at smaller scales in the southern half; however, it becomes distorted near the more massive condensations in the northern half. Notably, these condensations exhibit signs of impending collapse, as evidenced by supercritical mass-to-flux values. In the region S (i.e., the southern Hub: Hub-S), the magnetic field is considerably inhomogeneous among the detected condensations and we did not observe a direct correlation between the field morphology and the condensation density. Lastly, in an isolated dust clump located within a southern filament of Hub-N, the magnetic field aligns parallel to the elongated emission, suggesting a transition in the field geometry. Conclusions. The magnetic field shows a clear evolution with spatial scales. We propose that the most massive condensations detected in Hub-N are undergoing gravitational collapse, as revealed by the relative significance of the magnetic field and gravitational potential (Σ_B) and mass-to-flux ratio. The distortion of the magnetic field could be a response to the flow of material as a result of such a collapse.

Digging into the Interior of Hot Cores with ALMA (DIHCA). VI. The Formation of Low-mass Multiple Systems in High-mass Cluster-forming Regions

First Author: Luo, Qiu-yi
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00237.S, 2017.1.00101.S, 2018.1.00105.S, 2016.1.01036.S
BibCode: 2026ApJ...999..192L

Most stars form in multiple systems, with profound implications in numerous astronomical phenomena intrinsically linked to multiplicity. However, our knowledge about the process of how multiple stellar systems form is incomplete and biased toward nearby molecular clouds forming only low-mass stars, which are unrepresentative of the stellar population in the Galaxy. Most stars form within dense cores in clusters alongside high-mass stars (>8 M_⊙), as the Sun likely did. Here we report deep Atacama Large Millimeter/submillimeter Array (ALMA) 1.33 mm dust continuum observations at ∼160 au spatial resolution, revealing 72 low-mass multiple systems embedded in 23 high-mass cluster-forming regions, as part of the Digging into the Interior of Hot Cores with ALMA survey. We find that the companion separation distribution presents a distinct peak at ∼1200 au, in contrast to the one at ∼4000 au observed in nearby low-mass regions. The shorter fragmentation scale can be explained by considering the higher pressure exerted by the surrounding medium, which is higher than the one in low-mass regions, due to the larger turbulence and densities involved. Because the peak of the companion separation distribution occurs at much larger scales than the expected disk sizes, we argue that the observed fragmentation is produced by turbulent core fragmentation. Contrary to predictions, the multiplicity fraction remains constant as the stellar density increases. We propose that in the extremely dense environments where high-mass stars form, dynamical interactions play an important role in disrupting weakly bound systems.

A Monopolar Jet from Protostar HOPS 10: Evidence for Asymmetric Magnetized Launching

First Author: Dutta, Somnath
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2015.1.00041.S, 2018.1.00302.S
BibCode: 2026AJ....171..211D

A fundamental challenge in star formation is understanding how a protostar accretes mass from its circumstellar disk while removing excess angular momentum. Protostellar jets are widely invoked as the primary channels for angular-momentum removal, yet the mechanism by which they are launched and extract angular momentum remains poorly constrained. Here, we report high-resolution Atacama Large Millimeter/submillimeter Array Band 7 (345 GHz) and Band 6 (230 GHz) observations of ¹²CO (3─2), ¹²CO (2─1), and SiO (5─4) emission from the protostar HOPS 10 (G209.55−19.68S2). The combined data trace both the entrained outflow and the collimated jet with excellent spatial and velocity resolution, revealing a uniquely monopolar protostellar jet—the clearest example reported to date. The system exhibits a distinctly unipolar high-velocity jet (velocity offset, VHV,off=Vobserved−Vsystemic = +44 to +66 km s⁻¹), unlike the predominantly bipolar morphology characteristic of most protostellar jets. While the low-velocity outflow (velocity offset, V_LV,off = V_observed − V_systemic = −20 to +30 km s⁻¹) is detected in both directions, the high-velocity jet appears only on one side, and this monopolarity is consistent across all tracers. Given the nearly edge-on geometry and low submillimeter extinction, comparable emission would normally be expected from both lobes. The shock tracer SiO emission confirms a genuine, highly collimated jet rather than cloud contamination, and no ambient structure is capable of obscuring a counterjet. We argue that intrinsically asymmetric mass loading along the disk's magnetic field lines provides the most plausible explanation for the observed monopolarity.

Physical and Chemical Characterization of GY 91's Multi-ringed Protostellar Disk with ALMA

First Author: Jiang, Sally D.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2018.1.00028.S, 2021.1.01588.S
BibCode: 2026ApJ..1000...35J

GY 91, commonly categorized as a Class I young stellar object, is notable for disk dust substructures that have been hypothesized to trace early planet formation. Using the Atacama Large Millimeter/submillimeter Array 12 m and Atacama Compact Array, we present new Band 7 dust continuum and molecular line observations of GY 91 at an angular resolution of ∼0.″3 (40 au). We report detections of CS J = 6─5, N₂H⁺ J = 3─2, C¹⁸O J = 3─2, H₂CS JKa,Kc=81,7−71,6 , H₂CO JKa,Kc=40,4−30,3 , and H₂CO JKa,Kc=42,3−32,2 , as well as a tentative detection of ¹³C¹⁸O J = 3─2. We observe azimuthal asymmetry in CS and H₂CS emission, as well as radially structured H₂CO 4_0,4─3_0,3 emission outside the dust continuum. C¹⁸O and H₂CO 4_0,4─3_0,3 show significant cloud contamination, while CS and N₂H⁺ are good tracers of Keplerian rotation originating from the disk. Envelope emission does not appear to contribute significantly either to the continuum or molecular line observations. GY 91's chemical properties appear in large part to resemble those of Class II disks, although observations of additional molecular probes should be obtained for a fuller comparison. With CS, we estimated a dynamical stellar mass of 0.58 M_⊙, which is higher than previous estimates from stellar evolutionary models (0.25 M_⊙). Using both radiative transfer modeling of the dust continuum and comparison of the C¹⁸O and N₂H⁺ fluxes to literature thermochemical models, we estimate a disk mass of ∼0.01 M_⊙.

A JWST NIRCam/MIRI View of the W51A High-mass Star-forming Region

First Author: Yoo, Taehwa
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2015.1.01596.S, 2017.1.00293.S
BibCode: 2026AJ....171..208Y

We present observations of the W51A region, including the massive protoclusters W51-E and W51-IRS2, with JWST in 10 NIRCam and 5 MIRI filters. In this work, we highlight the most novel features apparent in these images and compare them with other multiwavelength images. The broad view of the NIRCam/MIRI images of the W51A region shows that areas dominated by warm dust and ionized gas are distinct from those dominated by polycyclic aromatic hydrocarbons. The high angular resolution of the JWST images resolves dust filaments in high contrast, revealing geometrically converging features feeding W51-E and a cavity around W51-IRS2. This picture adds support to the hypothesis that feedback from W51-IRS2 is suppressing further gas infall onto the protocluster, while by contrast, gas is still accreting onto W51-E. Comparing the NIRCam and MIRI images to Atacama Large Millimeter/submillimeter Array (ALMA) data, we find 24 sources detected by both JWST and ALMA, accounting for only ∼10% of the ALMA sources; the rest are too embedded or too cool to be detected by JWST. A knot of [Fe II] and H₂ emission north of W51-IRS2, previously detected in ground-based images, reveals peculiarly bright and compact peaks detected in all JWST bands. The knot is likely the most energetic example of a protostellar jet driven by a massive star impacting dense interstellar medium. The new images provide a complementary view to the previous long-wavelength perspective on this 4 × 8 pc area of one of the most active star-forming regions in our Galaxy, revealing new mysteries to be further explored.

The ALMaQUEST Survey. XVII. Unveiling Multiple Quenching Pathways in Green Valley Galaxies via Molecular Gas and Quenching Timescale Analyses

First Author: Lin, Lihwai
Instruments: ALMA_Band_3
ProgramIDs: 2015.1.01225.S, 2017.1.01093.S, 2018.1.00558.S, 2018.1.00541.S, 2019.1.00260.S, 2019.1.01136.S, 2019.1.01178.S
BibCode: 2026ApJ...999..263L

Statistically, green valley (GV) galaxies exhibit lower molecular gas fractions (f_gas) and reduced star formation efficiency (SFE) compared to star-forming galaxies. However, it remains unclear whether quenching is primarily driven by one factor or results from a combination of mechanisms in individual GV galaxies. In this study, we address this question by examining the spatial distributions of star formation and molecular gas in 28 GVs selected from the ALMaQUEST survey and additional literature samples. For each galaxy, we identify regions with suppressed specific star formation rate (sSFR) and measure ∆f_gas and ∆SFE—offsets from the resolved scaling relations of the star-forming main-sequence galaxies. By comparing the fraction of regions with negative ∆f_gas and ∆SFE, we classify 35.7% ± 13.2% (57.1% ± 17.9%) of GV galaxies as f_gas driven, 39.3% ± 14.0% (39.3% ± 14.0%) as SFE driven, and 25.0% ± 10.6% (3.6% ± 3.6%) as mixed mode when adopting a fixed (variable) CO-to-H₂ conversion factor (α_CO). These results indicate that GVs undergo quenching through multiple pathways. As sSFR decreases from the main sequence to the GV, we observe a transition toward predominantly SFE-driven quenching, possibly linked to internal processes such as morphological quenching or active galactic nucleus activity. We further estimate the quenching timescale (τ_decay), defined as the time from the peak star formation rate to 1 e^─1 (approximately 37%) of its value, using integrated MaNGA spectra. SFE-driven quenching is typically associated with short τ_decay, while f_gas-driven quenching shows a broader range. Overall, 75% of GVs exhibit τ_decay shorter than 1 Gyr, suggesting that quenching in most GVs proceeds rapidly, challenging purely slow-quenching scenarios like starvation.

Detailed lens modeling and kinematics of the submillimeter galaxy G09v1.97: An analysis of CO, H₂O, H₂O⁺, and dust continuum emission

First Author: Kade, K.
Instruments: ALMA_Band_4
ProgramIDs: 2015.1.01320.S, 2018.1.01710.S
BibCode: 2026A&A...707A.252K

Context. While the formation mechanisms of intensely starbursting galaxies at high redshift remain unknown, one possible mechanism for producing these intense rates of star formation is via mergers and interactions. However, detecting these at high redshift remains a challenge. Observations of high-redshift gravitationally lensed galaxies provide a way to study the interstellar medium and environment of these extreme starbursts in detail. Aims. We aim to use high angular resolution observations of dust continuum, CO(6−5), H₂O(2₁₁ − 2₀₂), and H₂O⁺(2₀₂ − 1₁₁) emission to constrain the ongoing processes in the z = 3.63 gravitationally lensed submillimeter galaxy H-ATLAS J083051.0+013224 (G09v1.97). Methods. We used the sophisticated lens modeling software PYAUTOLENS to perform both parametric and nonparametric source modeling. We created a demagnified source plane CO(6−5) emission line cube and performed the kinematic modeling using ^3DBAROLO. Additionally, we investigated the properties of the continuum and molecular line emission in the source plane. Results. We find that the regions of CO(6−5) and H₂O(2₁₁ − 2₀₂) emission are closely matched in the source plane, but that the dust continuum emission is more compact. We find that our lens modeling results do not require more than one source, contrary to what has been found in previous studies. Instead, we find that G09v1.97 resembles a rotating disk with V_max/σ̄ = 2.8 ± 0.4 V max / σ ̄ = 2.8 ± 0.4 , along with evidence of residual emission indicative of noncircular motions such as outflows, tidal tails, or an additional background galaxy. Conclusions. We suggest that the origin of the noncircular motions might be associated with a biconical outflow or a tidal tail from an interaction; alternatively, this might indicate the possible presence of an additional galaxy. We calculated the dynamical mass, gas mass, star formation rate, and depletion time for G09v1.97, along with a high star formation rate and low gas depletion time. In combination, this suggests that G09v1.97 has recently undergone an interaction, triggering intense star formation, while also being in the process of settling into a disk.

A persistent bow shock in a diskless magnetized accreting white dwarf

First Author: Iłkiewicz, Krystian
Instruments: MUSE
ProgramIDs: 112.25LQ
BibCode: 2026NatAs..10..391I

Stellar bow shocks form when an outflow interacts with the interstellar medium. In white dwarfs accreting from a binary companion, outflows are associated with strong winds from the donor star, the accretion disk or a thermonuclear runaway explosion on the white dwarf surface. To date, only six accreting white dwarfs are known to harbour disk-wind-driven bow shocks that are not associated with thermonuclear explosions. Here we report the discovery of a bow shock associated with a high-proper-motion diskless accreting white dwarf, 1RXS J052832.5+283824. We show that the white dwarf has a strong magnetic field in the range B ≈ 42-45 MG, making RXJ0528+2838 a bona fide known polar-type cataclysmic variable harbouring a bow shock. The resolved bow shock is shown to be inconsistent with a past thermonuclear explosion or with being inflated by a donor wind, ruling out all accepted scenarios for inflating a bow shock around this system. Modelling of the energetics reveals that the observed bow shock requires a persistent power source with a luminosity significantly exceeding the system accretion energy output. This implies the presence of a powerful, previously unrecognized energy-loss mechanism—potentially tied to magnetic activity—that may operate over sufficiently long timescales to influence the course of binary evolution.

Where Do Stars Explode in the ISM?—The Distribution of Dense Gas around Evolved Massive Stars in M33

First Author: Sarbadhicary, Sumit K.
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00901.S, 2019.1.01182.S, 2018.1.00378.S
BibCode: 2026ApJ..1000...70S

The effect of supernovae (SNe) on star formation in the interstellar medium (ISM) depends sensitively on where SNe explode with respect to ISM clouds. Observationally, SN ISM environments characterized by spatially resolved gas maps can empirically guide the placement of SNe in subgrid models, but unfortunately such measurements remain scarce, as SNe are rare and often distant. Here we demonstrate a new approach—mapping the ISM around evolved massive stars that are soon to explode. These provide a substantially larger sample of "explosion sites" (than just historical SNe) in nearby galaxies that have high-resolution atomic and molecular ISM maps from the Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. We demonstrate this technique in the well-resolved Local Group spiral M33 by analyzing the 50 pc scale projected ISM densities around red supergiants (RSGs; 8─30 M_⊙stars) Wolf─Rayet stars (W-Rs; >30M_⊙stars), and supernova remnants. We find a mass-dependent correlation between stars and gas clouds, with at least 45% of W-Rs and up to 77% of RSGs having no detectable H₂ at their pixel locations. In the sample with H₂ detections, we find that more-massive younger progenitors are coincident with denser gas. We show that the density distributions for stars >15 M_⊙are statistically distinct from random alignment of stars and gas in M33. Our work provides the first observationally derived estimate of the fraction of the SN-producing stellar population correlated with ISM density peaks. We demonstrate how this can be compared with galaxy simulations, and advocate similar comparisons to the community for constraining subgrid models.

The turbulence driving mode in NGC7793 and NGC1313

First Author: Miller, Lewis J.
Instruments: ALMA_Band_6
ProgramIDs: 2015.1.00782.S
BibCode: 2026MNRAS.547ag359M

We present spatially resolved measurements of turbulence driving modes across entire extragalactic discs of NGC7793 and NGC1313, using Atacama Large Millimetre/submillimetre Array (ALMA) CO (J = 2─1) observations at

$13\, \mathrm{pc}$

resolution. By applying a kernel-based analysis of density and velocity fluctuations, we map the turbulence driving parameter, b, which characterises the balance between solenoidal (

$b\sim 0.3$

) and compressive (

$b\sim 1$

) turbulent driving regimes. b is quantified as the ratio of the turbulent density fluctuations relative to the turbulent sonic Mach number,

$\mathcal {M}$

. Both galaxies show predominantly solenoidal driving on average for the regions where we find valid results (

$b\ge 0.33(\pm 0.05)^{+0.14}_{-0.10}$

in NGC7793;

$b\ge 0.24(\pm 0.03)^{+0.10}_{-0.07}$

in NGC1313), noting that this is without including the influences of magnetic fields, making these measurements lower limits. We find substantial spatial variation of b, including localized regions of strongly compressive driving. NGC1313 exhibits higher turbulent Mach numbers and density dispersions than NGC7793, consistent with the disturbed morphology and recent satellite interaction in NGC1313. The turbulence in both NGC7793 and NGC1313 is supersonic (

$3\lesssim \mathcal {M}\lesssim 20$

), and NGC1313 shows a radially decreasing trend of

$\mathcal {M}$

with galactocentric radius. Radial trends indicate more solenoidal driving in the galaxy centres, potentially reflecting enhanced shear, and increasingly compressive modes in the outskirts. These results demonstrate that turbulence driving varies systematically with galactic environment and cannot be assumed uniform across discs. Our study applies a previously established method to larger scales and new data, linking local turbulence physics to global star formation regulation in galaxies, providing a new avenue for testing theoretical models with future integral field units (IFU) and ALMA surveys.

Spatial distribution of organics in the Horsehead nebula: Signposts of chemistry driven by atomic carbon

First Author: Hernández-Vera, Claudio
Instruments: ALMA_Band_3
ProgramIDs: 2016.2.00027.S
BibCode: 2026A&A...707A.120H

Complex organic molecules (COMs) are considered essential precursors to prebiotic species in the interstellar and circumstellar medium. Despite their astrobiological relevance, many aspects of the formation of COMs remain unclear, particularly the role of ultraviolet (UV) radiation. While COMs were once expected to be efficiently destroyed under UV-irradiated conditions, detections in photodissociation regions (PDRs) have challenged this view. However, the mechanisms by which UV radiation contributes to their formation are still uncertain. Here we present moderately resolved maps of simple and complex organic molecules at the UV-illuminated edge of the Horsehead nebula, obtained by combining Atacama Large Millimeter/submillimeter Array (ALMA) and IRAM 30 m single-dish observations at ~15″ resolution. For the first time in this PDR environment, we analyzed the spatial distribution of species such as C¹⁷O, CH₂CO, CH₃CHO, HNCO, CH₃CN, and HC₃N. By incorporating previous C¹⁷O and C¹⁸O single-dish data as well as Plateau de Bure Interferometer (PdBI) maps of H₂CO and CH₃OH, we derived profiles of gas density, temperature, thermal pressure, and column densities of the organic species as a function of distance from the UV source. Our results show that most organic species ─ particularly H₂CO, CH₂CO, CH₃CHO, HNCO, and CH₃CN ─ exhibit enhanced column densities at the UV-illuminated edge compared to cloud interiors, possibly indicating efficient dust-grain surface chemistry driven by the diffusion of atomic C and radicals produced via photodissociation of CO and CH₃OH, as supported by recent laboratory experiments. The exceptions, HC₃N and CH₃OH, can be attributed to inefficient formation on dust grains and ineffective nonthermal desorption into the gas phase, respectively. Additionally, contributions from gas-phase hydrocarbon photochemistry, possibly seeded by grain-surface products, cannot be ruled out. Further chemical modeling is needed to confirm the efficiency of these pathways for the studied species, which could have important implications for other cold UV-irradiated environments such as protoplanetary disks.

ATOMS-QUARKS Survey: Inflow and Infall in Massive Protocluster G318.049+00.086— Evidence of Competitive Accretion

First Author: Gupta, Shivani
Instruments: ALMA_Band_3, ALMA_Band_7
ProgramIDs: 2019.1.00685.S, 2017.1.00545.S
BibCode: 2026ApJ...999..180G

We present a gas kinematic study of the massive protocluster G318.049+00.086. The protocluster is reported to contain 12 prestellar core candidates and four protostellar cores. Filamentary structures are identified using the 1.3 mm dust continuum map, with four of them converging into a dense central region, forming a hub-filament system. High velocity gradients (10─20 km s⁻¹ pc⁻¹) derived from position─velocity analysis of H¹³CO⁺ emission along three of those filaments are suggestive of mass inflow onto the central hub. A mass inflow rate higher than 10³ M_⊙ Myr⁻¹ along the filaments indicates that the central hub is capable of forming massive star(s). Investigation of H¹³CO⁺ and CCH spectral profiles revealed the majority of the cores having the characteristic blue asymmetric line profiles, a typical signature of gravitational collapse. The remaining few cores showed red asymmetric profiles, indicative of gas expansion. Also, the derived mass infall rates for the protostellar cores in the hub region are significantly higher in comparison to those located along the filaments. The mass─radius relation of the cores revealed that the cores with red profiles reside in the massive star formation regime. However, the global velocity gradient along the filaments suggests that these particular cores are losing material to the hub. Our results support a competitive accretion scenario of massive star formation where gas is expected to be funnelled from less gravitationally dominant cores to the cores located at the gravitationally favorable position.

Orbital Motions of Binaries in Orion South

First Author: Zapata, Luis A.
Instruments: ALMA_Band_3
ProgramIDs: 2018.1.01107.S
BibCode: 2026ApJ...999..219Z

We present high-angular resolution ( ≃0.″06 ) Very Large Array and Atacama Large Millimeter/submillimeter Array observations of Orion South separated by 15.52 yr. The purpose of this study was to search for orbital motions in three close ( ≃0.″1 ) binary systems in the region. We do not detect changes in the position angle of the binaries, but in two of the cases, we detect significant changes in their separation in the plane of the sky. We use these changes to estimate that the total mass of the binaries is in the ≃1─2 M_⊙ range. We also estimate the disk masses from the millimeter emission. The disk-to-stellar mass ratio is in the range of 0.04─0.18, values consistent with those expected for very early stellar evolution (Class 0) protostars.

Massive dusty multiphase outflow in local merger shows no sign of slowing on kiloparsec scales

First Author: Hagedorn, B.
Instruments: ALMA_Band_3, ALMA_Band_7, MUSE
ProgramIDs: 0103.B-0391, 2018.1.00888.S, 2013.1.00659.S
BibCode: 2026A&A...707A..77H

We use ALMA CO(1-0) observations and VLT/MUSE rest-frame optical data of the ultraluminous infrared galaxy (ULIRG) IRAS20100-4156 at z = 0.1297 to characterize its powerful outflow in multiple phases using tracers of cold molecular, ionized, and neutral atomic gas and dust as well. Our analysis uses the correspondence with the stellar velocity field to split the complex emission line profiles of the CO(1-0) line into components in gravitational and non-gravitational motion. We find a massive (8 × 10⁹ M_⊙) molecular outflow containing about 40% of the total molecular gas mass in the system. The outflow shows a bi-conical morphology centered on the brightest galaxy in the merger, oriented along its minor axis and extending to ∼5 kpc. This outflow has a characteristic velocity of 170 km/s, an outflow mass rate of 700 M_⊙/yr, a depletion time of 16 Myr, and energetics consistent with star formation as a driver. The neutral atomic and ionized gas phases traced by NaI absorption and Hα emission show counterparts to the blueshifted cold molecular outflow but are only 15% and 3% as massive. None of the three gas phases show any signs of slowing down over the extent at which we detected the outflow, suggesting an acceleration mechanism acting on the outflowing gas at kpc scales. We also detect 3.5 × 10⁷ M_⊙ of dust, traced by optical extinction in the MUSE data, in the blueshifted outflowing cold molecular gas. The ionization state of the non-outflowing gas is consistent with star formation, while the outflowing component shows shock-like ionization. We conclude that the multiphase outflow in IRAS20100-4156 originates in the southeast nucleus of the merger and is driven by the starburst activity there, with radiation pressure likely playing a significant role in its acceleration.

Bar-driven Shocks in NGC 1365 Revealed by the Most Luminous Extragalactic Class I Methanol Maser

First Author: Chen, Xi
Instruments: ALMA_Band_6, MUSE
ProgramIDs: 094.B-0321, 2021.1.01150.S
BibCode: 2026ApJ...999L..20C

We report the first detection of the 36.2 GHz (4₋₁ → 3₀ E) Class I methanol (CH₃OH) maser in the central region of the barred spiral galaxy NGC 1365. This detection using the Australia Telescope Compact Array establishes NGC 1365 as the host of the most luminous extragalactic Class I methanol maser known, with a total isotropic luminosity of 19.3 L_⊙. The maser emission is unambiguously localized to the southern arm of the circumnuclear starburst ring and exhibits a tight alignment with the bar-driven gas inflow lane. The striking absence of maser emission in the star formation and feedback-dominated northern arm reveals a fundamental bimodality within the ring. Combined with archival multiwavelength data, our results demonstrate that the maser traces low-velocity (∼25−30 km s⁻¹), nondissociative molecular shocks in the southern arm, where the gas is cold, dense, and subject to a weak radiation field. This work directly resolves the long-standing ambiguity between bar-driven shocks and stellar feedback, establishing the 36.2 GHz maser as a unique and powerful shock-specific diagnostic for extragalactic studies. It provides a novel tool to spatially pinpoint shock fronts and to disentangle the roles of gravitational dynamics and radiative feedback in shaping the extreme environments of galactic nuclei.

Digging into the Chemical Complexity in the Outer Galaxy: A Hot Molecular Core in Sh 2-283

First Author: Ikeda, Toki
Instruments: ALMA_Band_7
ProgramIDs: 2022.1.01270.S
BibCode: 2026ApJ...999..194I

The outer Galaxy (Galactocentric distance ≳13.5 kpc) serves as an excellent laboratory for investigating the chemical complexity in low-metallicity environments. Here we present the chemical analyses for the outer Galactic hot core Sh 2-283-1a SMM1 (D_GC = 15.7 kpc and Z ∼ 0.3 Z_⊙), recently detected by T. Ikeda et al. using the Atacama Large Millimeter/submillimeter Array. Toward this source, a variety of molecular species, including complex organic molecules (COMs; CH₃OH, ¹³CH₃OH, CH₂DOH, and CH₃OCH₃), are detected. The molecular abundances relative to CH₃OH are similar to those of another outer Galactic hot core, demonstrating that chemically rich hot cores exist in different regions of the outer Galaxy. We also compared molecular abundances among hot cores in the inner Galaxy, outer Galaxy, and Magellanic Clouds. This comparison revealed that the metallicity-corrected N(SO₂)/N(H₂) ratios of outer Galactic hot cores are significantly lower than those of the inner Galactic ones, while their N(CH₃OH)/N(H₂) ratios are similar. The Magellanic hot cores show different trends despite having metallicities similar to those of the outer Galaxy, indicating that the chemical complexity of hot cores is governed by environmental conditions (e.g., cosmic-ray intensity and dust temperature) rather than simple metallicity scaling. These environmental differences would also affect the production efficiency of COMs derived from CH₃OH, as the N(CH₃OCH₃)/N(CH₃OH) and N(C₂H₅OH)/N(CH₃OH) ratios in the outer Galactic sources are moderately lower than those of inner Galactic sources. The N(CH₂DOH)/N(CH₃OH) ratio of Sh 2-283-1a SMM1 is 1.5 −1.2+3.9 %, comparable to that of inner Galactic high-mass sources.

Older Ages for 23 Pre-main Sequence Stars in Upper Scorpius Using Dynamical-mass-constrained Stellar Evolutionary Models

First Author: Towner, A. P. M.
Instruments: ALMA_Band_7
ProgramIDs: 2019.1.00493.S
BibCode: 2026ApJ...999..145T

We present revised stellar ages for 23 pre-main-sequence (PMS) K- and M-type stars in the Upper Scorpius (Upper Sco) star-forming region, derived using stellar dynamical masses to constrain isochronal ages from five PMS stellar evolutionary models. We find that mass-constrained stellar ages for all model sets are more consistent with the older, ∼8─11 Myr age for Upper Sco derived using earlier-type stars. Additionally, applying the independent mass constraint to isochronal ages tends to (1) increase stellar ages for most model sets, and (2) decrease age scatter for individual sources between model sets. Models that account for global magnetic fields consistently provide the best match to our observations: they change comparatively little when the mass constraint is applied, and produce 9─10 Myr ages under both unconstrained and mass-constrained conditions. Most standard (nonmagnetic) models produce younger ages (3─5 Myr) when unconstrained, but older ages (6─9 Myr) when constrained by dynamical mass. Our results are consistent with recent literature findings that suggest median disk lifetimes may be ≳2× longer than previously thought.

Upper Limit on HF(1─0) Absorption in a Dusty Star-forming Galaxy at z = 6: Constraints on Early Fluorine Enrichment

First Author: Tsujita, Akiyoshi
Instruments: ALMA_Band_5
ProgramIDs: 2023.1.01281.S
BibCode: 2026ApJ...999L..14T

Wolf─Rayet (WR) stars have recently attracted attention as possible drivers of early chemical enrichment, including the production of fluorine, whose nucleosynthetic origin remains debated. To test the contribution of massive stars to fluorine production in the early Universe, we conducted Atacama Large Millimeter/submillimeter Array Band 5 spectroscopy of the HF(1─0) absorption line toward a dusty star-forming galaxy at z = 6.024. This galaxy has a known gas-phase metallicity and is too young for low-mass asymptotic giant branch stars to have contributed significantly, providing a clean environment to isolate massive-star yields. We do not detect significant HF absorption (∼2σ) and derive a conservative 5σ upper limit of NHF/NH2<2.2×10−9 . This limit is about an order of magnitude below typical local measurements, indicating inefficient fluorine enrichment ∼0.9 Gyr after the Big Bang. Comparison with chemical evolution models shows that our constraint is consistent with scenarios without WR yields at this epoch. Expanding the sample of HF absorption measurements in high-redshift galaxies with well-characterized metallicities will be crucial for tracing the onset of WR enrichment and fluorine production across cosmic time.

Spatially resolved star formation relations in local luminous infrared galaxies along the complete merger sequence

First Author: Sánchez-García, M.
Instruments: ALMA_Band_6
ProgramIDs: 2015.1.00714.S, 2013.1.00243.S, 2013.1.00271.S, 2017.1.00255.S, 2017.1.00395.S
BibCode: 2026A&A...707A.144S

We investigated the properties of the interstellar medium (ISM) at giant molecular cloud (GMC) scales (∼100 pc) in a sample of 27 nearby luminous infrared galaxies (LIRGs) spanning all interacting stages along the merger sequence, i.e. from isolated systems to late-stage mergers. In particular, we study the relations between star-formation (SF) and molecular gas surface density as a function of the interaction stage by (1) defining beam-sized (unresolved, line-of-sight) regions and (2) identifying actual gas clumps and physical structures within the galaxies. In total, we identify more than 4000 beam-sized CO-emitting regions defined on scales of ∼100 pc and more than 1000 molecular gas clumps in the sample. To map the distribution of molecular gas we used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the J = 2─1 CO transition, and to map the distribution of star formation we used the Hubble Space Telescope (HST) observations of the Paα or Paβ hydrogen recombination lines. We derived spatially resolved Kennicutt─Schmidt (KS) relations for each LIRG in the sample. When using beam-sized regions, we find that 67% of galaxies follow a single relation between Σ_SFR and Σ_H2. However, in the remaining galaxies, the relation splits into two branches ─ one characterised by higher Σ_SFR and Σ_H2, the other by lower value ─ indicating the presence of a duality in this relation. In contrast, when using physical gas clumps, the duality disappears and all galaxies show a single trend. These results provide two complementary perspectives when studying the star formation process. The first maximises the number statistics (beam-sized regions), and the second focuses on actual structures associated with gas clumps in which the measured sizes have a physical meaning. We also studied other ISM and clump properties as a function of the merger stage of the LIRG systems. We find that isolated galaxies and systems in early stages of interaction exhibit smaller amounts of gas and lower star formation rates (SFRs). As the merger progresses, however, the amount of gas in the central kiloparsecs of the galaxy undergoing the merger increases, along with the SFR, and the slope of the KS relation becomes steeper, indicating an increase in the SF efficiency of the molecular gas clumps. Clumps in late-stage mergers are predominantly located at small distances from the nucleus, confirming that most of the activity is concentrated in the central regions. Interestingly, the relation between the star formation efficiency and the boundedness parameter (which measures the effects of gravity against velocity dispersion) evolves from being roughly flat in the early stages of the merger to becoming positive in the final phases, indicating that clump self-gravity only starts to regulate the star formation process between the early and mid merger stages.

Direct Spectroscopic Confirmation of the Young Embedded Protoplanet WISPIT 2c

First Author: Lawlor, Chloe
Instruments: GRAVITY, SPHERE
ProgramIDs: 115.29HG, 114.27EK
BibCode: 2026ApJ..1000L..38L

WISPIT 2 is a nearby young star with a multiringed disk that was recently confirmed to host a ∼4.9 M_Jup gas giant planet embedded in a large (60 au) gap at a radial separation of 57 au from the host star. We confirm and characterize a second, close-in planet in the WISPIT 2 system using a combination of new Very Large Telescope/SPHERE H-band dual-polarization imaging and VLTI/GRAVITY K-band interferometric observations of the WISPIT 2 system. The GRAVITY detection is consistent with a point-like source while its extracted K-band spectrum shows CO band-head absorption at 2.3 μm and a continuum shape consistent with a young giant planet. From the GRAVITY data, we extract a medium resolution K-band spectrum of the companion and fit atmospheric model grids using the species tool with nested sampling to constrain its effective temperature, radius, and luminosity. We infer T_eff of 1500─2600 K, a radius of 0.91─2.2 R_Jup, and a luminosity of (−3.47)─(−3.63). Comparison with evolutionary tracks implies a mass range of 8─12 M_Jup, approximately twice as massive as the previously confirmed WISPIT 2b. The astrometry rules out a background source and marginally detects orbital motion of WISPIT 2 c, which needs further follow-up observations for confirmation. WISPIT 2 now becomes an analog to PDS 70, offering a second laboratory for studying the formation and early evolution of a multiplanet system within its natal disk.

The Chemical Diversity of Giant-planet Nurseries as Revealed by ALMA

First Author: Booth, Alice S.
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_5, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2011.0.00318.S, 2012.1.00303.S, 2012.1.00631.S, 2013.1.00305.S, 2013.1.00498.S, 2015.1.00657.S, 2016.1.00340.S, 2016.1.00344.S, 2016.1.00826.S, 2016.1.00884.S, 2016.A.00026.S, 2017.1.00492.S, 2017.1.00845.S, 2017.1.01404.S, 2017.1.01424.S, 2017.1.01545.S, 2018.1.01055.L, 2018.1.01429.S, 2021.1.00690.S, 2021.1.00738.S, 2021.1.01123.L, 2023.1.00252.S, 2023.1.00628.S, 2024.1.00446.S
BibCode: 2026AJ....171..128B

With the giant exoplanet occurrence rate peaking around stars of 1.5─2.0 solar masses (M_⊙), there is strong motivation to characterize the disks that set their formation conditions. Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) allow us to investigate both the availability of different molecules in disks and infer the radial distribution of elemental abundances, enabling us to make connections to exoplanet systems. Here we present a survey of six transition disks around young F-, A-, and B-type stars using ALMA. We find ¹³C¹⁸O, CS, SO, and H₂CO in all six systems, as well as 10 additional molecules in a subset of disks, including detections of H₂S, ³³SO, and CH₃OCH₃. Using these data, and literature data where available, we construct the first comprehensive picture of Herbig disk chemistry. We find clear correlations between molecular tracers of C/O > 1 environments (e.g., CS, C₂H) and disk mass, as traced by C¹⁸O line flux. In contrast, tracers of C/O < 1 environments (e.g., SO, CH₃OH) do not show significant correlations with disk mass. Interestingly, these molecules are relatively brighter in lower-mass disks, with their presence primarily linked to disks with central cavities and spirals. Finally, we show that the observed chemical diversity seen across Herbig disks leads to varying C/O regimes at the orbital radii of candidate protoplanets identified within these disks. When comparing these inferred disk C/O ratios with those measured for directly imaged exoplanets, we find a notable overlap and show that low C/O gas is common on tens of au scales in Herbig disks.

A near-infrared and optical study of NGC 5822: an open cluster hosting barium-stars and lithium-enriched giant stars

First Author: Holanda, N.
Instruments: FEROS
ProgramIDs: unknownID
BibCode: 2026MNRAS.546f2286H

We present a chemical abundance study of giant stars in the Galactic open cluster NGC 5822, which hosts two barium stars (#002 and #201) and three lithium-enriched giants (#006, #102, and #240). Using high-resolution optical and near-infrared (H and K band) spectra from FEROS and IGRINS, we determine atmospheric parameters and abundances for 23 elements (Li, C, N, O, F, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, Cr, Fe, Ni, Y, Ce, Nd, Yb, and Pb). This includes species not yet studied in this cluster, such as F, P, K, Yb, and Pb, as well as oxygen isotopic ratios

$^{16}$

$^{17}$

O and

$^{16}$

$^{18}$

O. Membership was assessed using astrometry and chemical abundances, providing insight into the evolutionary stages of Li-enriched giants and cluster parameters (age, distance, extinction). However, the identification of Ba-stars remains challenging due to their binary nature and less reliable astrometric solutions. The cluster's abundances are broadly consistent with expectations for the Galactic thin disc. The mean fluorine abundance agrees with chemical evolution models predicting that young clusters (<2 Gyr) exhibit elevated [F/Fe], with production from SN II, SN Ia, AGB, and Wolf─Rayet stars. No distinct chemical or rotational features were found to explain the lithium enrichment, likely occurring either during the red clump phase or near the RGB tip. For the Ba-stars, nucleosynthesis models combined with the cluster's turn-off mass suggest polluting companion masses of 3.00 and 3.75

${\rm M}_{\odot }$

for stars #002 and #201. These results highlight the importance of open clusters as laboratories for chemically peculiar stars.

A Search for Late-type Brown Dwarfs in the Euclid Quick Data Release 1

First Author: Kiwy, Frank
Instruments: VIRCAM
ProgramIDs: 179.A-2010, 179.A-2004
BibCode: 2026AJ....171..108K

We present the identification and characterization of 15 mid-to-late T dwarf candidates in the Euclid Quick Release 1 (Q1) data set, based on a combined photometric and spectroscopic analysis. Candidates were initially selected via color-based cuts in the Euclid Y_E − J_E and J_E − H_E color─color space, targeting the region occupied by ultracool dwarfs (UCDs) in synthetic photometry from the A. Sanghi et al. sample. From an initial pool of 38,845 sources, we extracted low-resolution near-infrared spectra from the Euclid Near-Infrared Spectrometer and Photometer instrument and applied a two-stage validation procedure that included spectral template fitting followed by visual inspection. Eight of the 15 validated candidates are newly identified objects with no prior literature association. We examined their morphological and photometric properties, and compared them with established spectral standards. Photometric distances were derived using band-averaged distance modulus estimates. We discuss the limitations and promise of the Euclid survey for UCD studies, and demonstrate the potential for discovering substellar populations beyond the reach of current wide-field surveys.

Astrometric and Spectroscopic Analysis of IC 2714: An Open Cluster Hosting a Lithium-rich Giant

First Author: Flaulhabe, T.
Instruments: FEROS
ProgramIDs: unknownID
BibCode: 2026ApJ...997..288F

Open clusters serve as laboratories to study and evaluate stellar evolution and Galactic chemical evolution models. Chemical peculiarities, such as lithium-rich giants, are rarely observed in these stellar systems. This work focuses on eight red giants (#005, #028, #034, #053, #087, #121, #126, and #190) previously reported as members of the Galactic cluster IC 2714. We conducted a detailed investigation using high-resolution spectroscopy, supplemented with data from the Gaia DR3 catalog. Besides deriving the cluster's fundamental parameters, we provide the most thorough chemical characterization of IC 2714 to date, reporting the abundance of 23 species, including light elements (Li, C, N, O), odd-Z elements (Na, Al), α-elements (Si, Ca, Ti, Mg), iron-peak elements (Sc, Cr, Ni), s-process-dominated elements (Y, Zr, Ba, La, Ce, Nd) and r-process elements (Sm, Eu). We also present the carbon isotopic ratios ¹²C/¹³C for the first time for seven stars. One particular star (#087) exhibits a high lithium abundance ( log∊ (Li)_NLTE = +1.54 dex) and a slightly higher projected rotational velocity ( vsini = 6.7 km s⁻¹). Our results suggest that the analyzed stars are in the core-helium-burning phase of evolution, where the most lithium-rich giants are found. Combining astrometric probabilities and chemical abundances, we conclude that two giants (#028 and #034) might not be cluster members.

Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES⁺ observations

First Author: Pelaez-Torres, A.
Instruments: CRIRES
ProgramIDs: 110.2492
BibCode: 2026A&A...705A.256P

Context. Transmission spectra of Neptune-sized exoplanets are frequently observed to be featureless at low-to-mid resolutions from space; whereas high-altitude clouds can mute spectral features, high atmospheric metallicities can also result in compressed envelopes, where low scale heights may also yield undetectable signatures. Aims. We aim to study the atmospheric properties of the warm Neptune GJ 436 b by combining a set of five transit events observed with the CARMENES spectrograph with one transit from CRIRES⁺ so as to provide the most constrained results possible at high resolution. Methods. We removed telluric and stellar signals from the data using SysRem and potential planetary signals were investigated using the cross-correlation technique. Following standard procedures for undetected species, we performed injection recovery tests and Bayesian retrievals to place constraints on the detectability of the main near-infrared absorbers. In addition, we simulated ELT/ANDES observations by computing end-to-end in silico datasets with EXoPLORE. Results. No molecular signals were detected in the atmosphere of GJ 436 b, which is consistent with previous studies. Combined CARMENES-CRIRES⁺ injection-recovery and Bayesian retrieval analyses show that the atmosphere is likely covered by high-altitude clouds (~1 mbar) at low and intermediate metallicities or, alternatively, is very metal-rich (≳ 900× solar), which would suppress spectral features without invoking clouds. Simulations of ELT/ANDES observations suggest a boost by nearly an order of magnitude to the upper limit in the photon-limited regime, reaching 0.1 mbar at 10-300× solar metallicities. Conclusions. The joint analysis of all useful transit observations from CARMENES and CRIRES⁺ provides the most stringent constraints to date on the atmospheric properties of GJ 436 b. Complementary CCF-based and retrieval approaches consistently indicate that the atmosphere is either cloudy or highly metal enriched. Any weak near-infrared absorption lines, if present, are likely to be below current detection limits. However, according to our simulations, these features may be revealed with ELT/ANDES even in single-transit observations.

Dissecting the dust distribution and polarization around two B213 young stellar objects with ALMA

First Author: Sato, Asako
Instruments: ALMA_Band_3, ALMA_Band_6
ProgramIDs: 2021.1.01420.S, 2019.1.01209.S
BibCode: 2026A&A...706A.292S

Context. The pristine stages of disk formation during the protostellar phase and the processes of dust evolution in young disks remain largely unconstrained. Dust thermal emission at millimeter wavelengths and its polarization offer key insights into the physical processes and spatial distribution of material at the envelope-disk interface, as well as on early dust evolution around solar-type protostars. Aims. We characterize the dust properties and polarization mechanisms from envelope to disk scales in two young stellar objects (YSOs), IRAS 04166+2706 (K04166) and IRAS 04169+2702 (K04169) embedded in the same Taurus filament. We explore the nature of the dust polarization across scales and investigate their stage of evolution. Methods. We present deep (∼1.4 mm and ∼3 mm) polarimetric observations sampling the dust emission from 25 au to 3000 au using the Atacama Large Millimeter/submillimeter Array (ALMA). We modeled Stokes I emission to characterize disk and envelope contributions, while the polarization properties were analyzed to identify the dominant polarization mechanisms. Finally, in this work, we discuss the physical properties of both sources across scales. Results. K04166 shows extended Stokes I and polarized emission tracing a tentative hourglass magnetic field morphology in its envelope. In the inner envelope and disk (<100 au), the properties of the polarized emission change, suggesting the presence of a toroidal magnetic field around the disk or the presence of large grains in the inner envelope. K04169 exhibits compact Stokes I and polarized emission, consistent with self-scattering from the disk. Both disks are extremely compact, yet K04166 retains a substantial envelope while the one of K04169 is largely dissipated. Conclusions. Our multiscale ALMA polarimetric observations reveal a transition from magnetically aligned grains in envelopes to self-scattering in disks within the transition region of 20─50 au. These results provide important clues on dust grain growth and magnetic field morphology at the disk-envelope scales. The two sources, separated by <0.5 pc and embedded in a common filament, display striking differences, indicating that K04166 is a young embedded object with a substantial envelope threaded by relatively organized magnetic fields. Meanwhile, K04169 is more evolved, likely to be a young T-Tauri star. However, in both disks, the presence of large grains already suggest a scenario of early dust evolution in disks of the Class 0 stage.

Discovery of Multiple Ultra-broad-velocity Molecular Features Associated with the W44 Molecular Cloud

First Author: Makita, Momoko
Instruments: ALMA_Band_7
ProgramIDs: 2016.1.01548.S
BibCode: 2026ApJ...999L...3M

We report the discovery of multiple compact molecular features exhibiting extremely broad velocity widths toward the W44 molecular cloud. Atacama Large Millimeter/submillimeter Array CO J = 3─2 data reveal eight "Petit-Bullets" surrounding the previously known "Bullet." Each Petit-Bullet shows a distinct V-shaped structure in position─velocity space, reminiscent of the Y-shaped morphology of the Bullet, suggesting a common origin. These features are interpreted as the result of high-velocity plunges of compact gravitational objects into dense molecular gas. The spatial and kinematic properties of the Petit-Bullets suggest that the plunging material was not a single object but rather a small cluster of compact bodies. A virial mass of 1.0 × 10⁵ M_⊙ inferred from their velocity dispersion is comparable to that of typical globular clusters. Momentum analysis further implies that the main Bullet likely formed by an isolated black hole. These findings provide new evidence for dynamical interactions between halo clusters and disk molecular gas.

A Multiwavelength ALMA View of Gas and Dust in Binary Protoplanetary System AS 205: Evidence of Dust Asymmetric Distribution

First Author: Phuong, Nguyen Thi
Instruments: ALMA_Band_3, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2016.1.00484.L, 2018.1.01198.S, 2015.1.00168.S
BibCode: 2026ApJ...999...76P

We present Atacama Large Millimeter/submillimeter Array observations of multiwavelength dust emissions at 3.1 and 1.3 mm, along with molecular line emissions of CO(2─1), CO(3─2), ¹³CO(3─2), and C¹⁸O(3─2) at spatial resolutions of 7─45 au toward the protoplanetary system AS 205. The dust emissions exhibit two distinct components of AS 205 N and AS 205 S, separated by 1 .″ 3. While gas kinematics within the dust disk regions are dominated by Keplerian rotation, the more extended gas emission displays complex morphology and kinematics strongly affected by the binary gravitational interaction in the outer regions. The stellar masses of AS 205 N and AS 205 S are estimated at 0.78 ± 0.19 and 1.93 ± 0.86 M_⊙, respectively. Azimuthal variation is observed in the spectral index distribution of both disks. In AS 205 N, the spectral index minimum in the southwest is coincident with the peaks of CO(2─1), CO(3─2), and ¹³CO(3─2) integrated intensity and the relative position of its southern counterpart. On the other hand, the spectral index distribution in AS 205 S exhibits two prominent maxima, with the one in the northeast aligning with the peak of ¹³CO(3─2), and the peak in the south coinciding with local maxima in CO(2─1) and CO(3─2) azimuthal profiles. These results suggest a correlation between dust grain size and/or optical depth with the gas distributions. Dust trapping along the spiral arms possibly contributes to the spectral index minima in AS 205 N; however, the observed asymmetry across both disks suggests the involvement of additional mechanisms.

Cloud─Cloud Collisions Induce Filament-mediated Super Star Cluster Formation in the Antennae Overlap Region: Evidence from ALMA and JWST

First Author: Michiyama, Tomonari
Instruments: ALMA_Band_3
ProgramIDs: 2022.A.00032.S
BibCode: 2026ApJ...999..119M

The formation of super star clusters (SSCs) in galaxies remains a fundamental yet unresolved problem. Among the proposed mechanisms, cloud─cloud collisions (CCCs) have been suggested as a potential trigger, although observational validation has been limited. Here we present high-resolution ( 0.″12 , ∼14 pc) Atacama Large Millimeter/submillimeter Array observations of CO (J = 1─0) emission toward a super giant molecular cloud (SGMC) in the overlap region of the Antennae galaxies. The data resolve the SGMC into two distinct velocity components separated by ∼50 km s⁻¹. One component exhibits a "U"-shaped structure within a large filament likely shaped by ram pressure, while the other shows hub-filament morphology. Such a morphology is naturally interpreted as a CCC scenario. The 108 GHz continuum emission detected at the apparent collision interface is dominated by free─free radiation, with an ionizing photon rate consistent with the stellar mass and age of the optically identified SSCs. Supplementary infrared imaging with JWST reveals emission spatially coincident with the inferred collision interface, further supporting the CCC scenario. These results provide compelling, multiwavelength evidence that CCCs play a key role in triggering SSC formation in merging galaxies.

HOPS-288: A Laboratory for Complex Organics in Proto-binary/Proto-multiple Systems

First Author: Hsu, Shih-Ying
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00302.S, 2018.1.01038.S
BibCode: 2026ApJ...999...62H

Complex organic molecules (COMs) in young stellar objects have attracted significant attention in recent years due to their potential connection to prebiotic chemistry and their utility as tracers of warm or shocked gas components. Proto-binary and multiple systems with close separations are particularly valuable targets for investigating chemical inheritance and reaction, as their members are expected to form from similar material in their parental cloud. We present Atacama Large Millimeter/submillimeter Array observations of the hierarchical proto-triple system HOPS-288, focusing on the physical structure, kinematics, and COM compositions. The system is treated as a proto-binary system consisting of HOPS-288-A and HOPS-288-B due to the limited spatial resolutions, with a separation of 200 au. Three COM-rich features are revealed: two hot corinos associated with the two members, rich in a variety of COMs, and an intervening component between the two members traced by CH₃OH and tentatively by CH₃CHO. The hot corino in HOPS-288-A exhibits rotational features and might trace a disk. The hot corino in HOPS-288-B is also possibly exhibiting rotational motion. The intervening component could possibly trace a shocked region in the circumbinary disk or a bridge between the two members. The column densities of COMs, including ¹³CH₃OH, CH₂DOH, CH₃CHO, HCOOCH₃, C₂H₅OH, ¹³CH₃CN, and NH₂CHO, are broadly similar between the two sources, possibly suggesting the complex organic similarities among proto-binary/multiple systems. Given the complexity of the studied physical structures, further detailed investigations will be essential to confirm this result.

B-field Orion Protostellar Survey (BOPS). IV. The Relative Orientation between Magnetic Fields and Density Structures in Young Protostellar Envelopes

First Author: Cai, Kexin
Instruments: ALMA_Band_7
ProgramIDs: 2019.1.00086.S
BibCode: 2026ApJ...999..126C

We investigate the relative alignment between density structures and magnetic fields in eight young protostars from the Atacama Large Millimeter/submillimeter Array B-field Orion Protostellar Survey. Column density maps are derived from 870 μm dust continuum emission, and the Histogram of Relative Orientations method is applied to quantify the correlation between magnetic field orientations and density structures on envelope scales (∼10³ au). We find that the relative alignment shows overall little evidence of systematic evolution with column density, suggesting that column density alone does not fully determine the alignment. The magnetization level also plays a crucial role, with weakly magnetized envelopes exhibiting predominantly parallel or random alignment, whereas strongly magnetized ones show perpendicular configurations even at moderate densities. These results reveal that density and magnetization jointly shape the morphology of protostellar envelopes and the coupling between gravity and magnetic fields during early stages of star formation.

The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: 5σ Source Catalog and Redshift Distribution

First Author: Long, Arianna S.
Instruments: ALMA_Band_3, ALMA_Band_4
ProgramIDs: 2021.1.00246.S, 2021.1.00225.S, 2019.1.01600.S
BibCode: 2026ApJ...999...47L

One of the greatest challenges in galaxy evolution over the last decade has been constraining the prevalence of heavily dust-obscured galaxies in the early Universe. At z > 3, these galaxies are increasingly rare, and difficult to identify, as they are interspersed among the more numerous dust-obscured galaxy population at z = 1─3, making efforts to secure confident spectroscopic redshifts expensive, and sometimes unsuccessful. In this work, we present the Extended Mapping Obscuration to Reionization with the Atacama Large Millimeter/submillimeter Array (ALMA; Ex-MORA) Survey—a 2 mm blank-field survey in the COSMOS-Web field, and the largest ever ALMA blank-field survey to date, covering 577 arcmin². Ex-MORA is an expansion of the MORA survey designed to identify primarily z > 3 dusty, star-forming galaxies while simultaneously filtering out the more numerous z < 3 population by leveraging the very negative K-correction at observed-frame 2 mm. We identify 37 significant (>5σ) sources, 33 of which are robust thermal dust emitters. We measure a median redshift of <z>=3.8−1.52+1.7 , with two-thirds of the sample at z > 3, and just under half at z > 4, demonstrating the overall success of the 2 mm selection technique. The total integrated z > 3 volume density of Ex-MORA sources is ∼1─3 × 10⁻⁵ Mpc⁻³, consistent with other surveys of infrared luminous galaxies at similar epochs. We also find that techniques using rest-frame optical emission (or lack thereof) to identify z > 3 heavily dust-obscured galaxies miss at least half of Ex-MORA galaxies. This supports the idea that the dusty galaxy population is heterogeneous, and that synergies across observatories spanning multiple energy regimes are critical to understanding their formation and evolution at z > 3.

Digging into the Interior of Hot Cores with ALMA (DIHCA). VII. Disk Candidates around High-mass Stars and Evidence of Anisotropic Infall

First Author: Olguin, Fernando A.
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.01036.S, 2017.1.00237.S
BibCode: 2026ApJ...999..106O

We study the kinematics of condensations in 30 fields forming high-mass stars with the Atacama Large Millimeter/submillimeter Array at a high resolution of ∼0.″08 on average (∼230 au). The presence of disks is important for feeding high-mass stars without feedback halting growth as their masses increase. In the search for velocity gradients resembling rotation that can reveal the presence of disks, we analyze the emission of gas tracers in 49 objects using CH₃OH, CH₃CN, and tentative detections of HNCO and cis-HCOOH. Most of the velocity distributions show velocity gradients indicative of rotation. We reveal a total of 32 disk candidates, the largest sample to date that has been uniformly analyzed at a few hundred astronomical unit scales in the high-mass regime. Their position─velocity maps are generally asymmetric with one side brighter than the opposite. We successfully fit a power law to the position─velocity maps of the disk candidates and find indices between −0.5 (Keplerian rotation) and −1 (rotation under specific angular momentum conservation) with a median of −0.7. Under Keplerian rotation assumption, we estimate central masses, uncorrected for inclination, ranging between 7 and 45 M_⊙. Excluding outliers, the disk candidates are relatively more compact (<200 au) and less massive (<5 M_⊙) than previous results at coarser angular resolution. We calculate an average Toomre-Q parameter and find that most are gravitationally unstable (median of 0.5). We conclude that these observations offer the first opportunity to separate the disk and envelope components of hot cores on a statistically significant sample, and confirm that anisotropic collapse plays a role in feeding high-mass (proto)stars.

Constraining Properties of Dust Formed in Wolf─Rayet Binary WR 112 Using Mid-infrared and Millimeter Observations

First Author: Wu, Donglin
Instruments: ALMA_Band_6
ProgramIDs: 2023.1.00999.S, 2024.1.00803.S
BibCode: 2026ApJ...999...32W

Binaries that host a carbon-rich Wolf─Rayet (WC) star and an OB-type companion can be copious dust producers. Yet the properties of dust, particularly the grain size distribution, in these systems remain uncertain. We present Band 6 observations of WR 112 by the Atacama Large Millimeter/submillimeter Array telescope (ALMA), which are the first millimeter observations of a WC binary system capable of resolving its dust emission. By combining ALMA observations with James Webb Space Telescope images, we were able to analyze the spatially resolved spectral energy distribution (SED) of WR 112. We found that the SEDs are consistent with emissions from hydrogen-poor amorphous carbon grains. Notably, our results also suggest that the majority of grains in the system have radii below one micrometer, and the extended dust structures are dominated by nanometer-sized grains. Among four parameterizations of the grain radius distribution that we tested, a bimodal distribution, with abundant nanometer-sized grains and a secondary population of 0.1 μm grains, best reproduces the observed SED. This bimodal distribution helps to reconcile the previously conflicting grain size estimates reported for WR 112 and for other WC systems. We hypothesize that dust destruction mechanisms such as radiative torque disruption and radiative-driven sublimation are responsible for driving the system to the bimodal grain size distribution.

Early Planet Formation in Embedded Disks (eDisk). XIX. Structures of Molecular Outflows

First Author: Feeney-Johansson, Anton
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00261.L, 2019.A.00034.S, 2015.1.01512.S
BibCode: 2026AJ....171..172F

As part of the ALMA Large Program "Early Planet Formation in Embedded Disks," ¹²CO (2─1) was observed towards 19 nearby low-mass protostars. Of these objects, 15 sources are found to show molecular outflow emission. Based on their morphological and kinematical structures, the CO outflows are classified into three types: a wind-driven shell, where ambient material is swept up by a wide-angle wind from the star, a bow shock, and a slow disk wind, which is a conical or parabolic flow with onion-like velocity structure. We categorize 11 outflows as a slow disk wind, 7 as a wind-driven shell, and 1 as a bow shock. Four of these outflows were found to show signs of both slow disk wind and wind-driven shell characteristics. Five objects show misalignment between the red- and blueshifted outflows. Seven objects show significant misalignment between the outflow axis (either or both of the red- and blueshifted outflows) and the minor axis of the dust continuum emission around the protostar. For the objects showing wind-driven shell emission, we compare simple parametrized models with the observations to derive physical properties of the observed shells, such as their dynamical ages. This shows evidence of a time variability in the outflows, such as changes in their direction. In some objects, large differences are seen between the properties of the red- and blueshifted outflows, possibly indicating differences in the properties of the ambient medium with which the outflow interacts.

Silicon monoxide in the filamentary infrared dark cloud G035.39-00.33: An ALMA view

First Author: Liu, Rong
Instruments: ALMA_Band_3
ProgramIDs: 2016.1.01363.S
BibCode: 2026A&A...706A.328L

Aims. Filamentary infrared dark clouds (IRDCs) are believed to represent the initial conditions for massive star and cluster formation. Methods. We investigated the IRDC G035.39-00.33 using SiO, H¹³CO⁺, CH₃OH, and CS emission observed with ALMA at 3.5″ resolution (∼0.05 pc). The analysis of the SiO emission provides a record of shock activity within the cloud, offering insights into both the current level of star formation and the cloud's formation mechanisms. Results. We identify several regions with broad SiO emission clearly associated with outflows, pinpointing the locations of ongoing star formation across the cloud. The ALMA images also reveal a series of spatially extended SiO emission spots with narrow line profiles aligned along an arc-like path that is also seen in CS and CH₃OH emission. While the broad SiO emission is mainly associated with the main cloud filament, as seen in visual extinction, the narrow SiO arch is located at the edge of the cloud, far from the identified sites of star formation activity. The presence of these arc-like morphologies suggests that large-scale shocks may have compressed the gas in the surroundings of the G035.39-00.33 cloud, shaping its filamentary structure. By inspecting the large-scale radio continuum emission around G035.39-00.33, we find that this IRDC is part of a larger star-forming complex where the densest and coolest material appears at the interacting regions between a supernova remnant (SNR) and an expanding HII region. In particular, we hypothesise that this IRDC may be spatially coincident with the ionised expanding gas associated with the previously identified SNR G35.6-0.4. Conclusions. We suggest that collisions between giant molecular clouds and expanding gas flows from interacting SNRs and HII regions may be responsible for the observed arc-like structures. Such shock compressions could play an important role in the formation of IRDCs and in the potential triggering of star formation.

The Cosmic Owl: Twin Active Collisional Ring Galaxies with Starburst Merging Front at z = 1.14

First Author: Li, Mingyu
Instruments: ALMA_Band_6
ProgramIDs: 2016.1.01040.S
BibCode: 2026ApJ...999...40L

Galaxy mergers play a critical role in driving galaxy evolution, especially by transforming galaxy morphology, redistributing gas around galaxies, triggering active galactic nuclei (AGN), and stimulating star formation. We present the Cosmic Owl, a galaxy merger at z = 1.14, identified in the COSMOS field. Deep imaging and spectroscopy from JWST, the Atacama Large Millimeter/submillimeter Array, and the Very Large Array reveal a complex system of twin collisional ring galaxies, exhibiting nearly identical morphologies. The grism spectra from the JWST COSMOS-3D program confirm that both galaxies host an AGN. A bipolar radio jet from one AGN extends to strike the merging front. In addition, we detect a starburst at the merging front, characterized by luminous extended nebular line emission and a massive cold gas reservoir. This starburst is likely triggered by interstellar shocks induced by galaxy collision and the AGN jet. The twin ring structure of the Cosmic Owl requires further numerical simulations to clarify the precise conditions that lead to the formation of this rare morphology. This system exemplifies how shock-induced star formation, driven by galaxy collision or AGN jet, can act as a crucial mechanism for triggering intense starbursts in the early Universe.

Interaction of the central jet with the surrounding gas in the protostellar outflow from IRAS 04166+2706

First Author: Tafalla, M.
Instruments: ALMA_Band_6
ProgramIDs: 2021.1.00575.S
BibCode: 2026A&A...706A.248T

Context. The outflow from the Class 0 protostar IRAS 04166+2706 (hereafter IRAS 04166) contains a remarkably symmetric jet-like component of extremely high-velocity (EHV) gas. Aims. We studied the IRAS 04166 outflow and investigated the relation between its EHV component and the slower outflow gas. Methods. We mosaicked the CO(2─1) emission from the IRAS 04166 outflow using the 12m and the Compact Arrays of ALMA. We also developed a ballistic toy model of the gas ejected laterally from a jet to interpret the data. Results. In agreement with previous observations, the ALMA data show that the slow outflow component is distributed in two opposed conical lobes and has a shear-flow pattern with velocity increasing toward the axis. The EHV gas consists of a series of arc-like condensations that span the full width of the conical lobes and merge with their walls, suggesting that the fast and slow outflow components are physically connected. In addition, position─velocity diagrams along the outflow axis show finger-like extensions that connect the EHV emission with the origin of the diagram, as if part of the EHV gas had been decelerated by its interaction with the low-velocity outflow. A ballistic model can reproduce these finger-like extensions assuming that the EHV gas consists of jet material that has been ejected laterally over a short period of time and has transferred part of its momentum to the surrounding shear flow. Conclusions. The EHV gas in the IRAS 04166 outflow seems to play a role in the acceleration of the slower gas component. The presence of similar finger-like extensions in the position─velocity diagrams of other outflows suggests that this process may be occurring in other systems, even if the EHV component is not seen because it has an atomic composition.

Evidence of Gas Depletion in Quasars with Moderate Radio Emission

First Author: Wen, Yuhan
Instruments: ALMA_Band_7
ProgramIDs: 2016.2.00060.S, 2022.1.00029.S
BibCode: 2026ApJ...998..323W

The energy released by active galactic nuclei (AGNs) is considered to have a profound impact on the cold gas properties of their host galaxies, potentially heating or removing the gas and further suppressing star formation. To understand the feedback from AGN radio activity, we investigate its impacts on the cold gas reservoirs in AGNs with different radio activity levels. We construct a quasar sample with a mean z ∼ 1.5 and a mean L_bol ∼ 10^45.8 erg s⁻¹, all with Herschel detections to enable estimates of the total gas mass through the galactic dust continuum emission. The sample is then crossmatched with radio catalogs and divided into radio-loud quasars, radio-detected radio-quiet (RQ) quasars, and radio-undetected quasars based on their radio loudness. Through spectral energy distribution fitting, we find the radio-detected RQ quasars exhibit evidence of gas deficiency with host galaxies possessing ∼0.3 dex lower dust and gas masses compared to the other two groups, despite being matched in M_BH, L_bol, M_*, and star formation rate. Furthermore, evidence from optical spectra shows that both the fraction and velocity of outflows are higher in the radio-detected RQ group, suggesting a connection between the ionized gas outflows and the moderate radio activity. These results suggest that the AGN feedback could be more efficient in AGNs with weak/moderate radio emission than in those without radio detection or those with strong radio emission. Further high-resolution observations are needed to understand the interaction between the interstellar medium and the weak/moderate AGN radio activity.

ALMA Polarization Study of the Magnetic Fields in Two Massive Clumps in the 20 km s⁻¹ Cloud of the Central Molecular Zone

First Author: Liu, Yuhua
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.00286.S
BibCode: 2026ApJ...998..330L

We present the Atacama Large Millimeter/submillimeter Array observations of linearly polarized 870 μm continuum emission at ∼0 .″ 2 (2000 au) resolutions toward the two massive clumps, Clump 1 and Clump 4, in the 20 km s⁻¹ cloud. The derived magnetic field strength for both clumps ranges from ∼0.3 to 3.1 mG using the angular dispersion function method. The magnetic field orientations across multiple scales suggest that the magnetic field dominates at the cloud scale, whereas gravity appears to govern structures at the core (0.01−0.1 pc) and condensation (≤0.01 pc) scales. Furthermore, the study on the angular difference between the orientations of the local gravity gradient and the magnetic field suggests that the magnetic field predominantly governs the dynamics in the diffuse regions, while gravity and star formation feedback become increasingly significant within the dense regions. The ratio of the magnetic field tension force F_B to the gravitational force F_G suggests that the magnetic field may provide some support against gravity, but it is insufficient to prevent gas from infalling toward the dense cores.

ALMAGAL. VII. Cataloging Hierarchical Continuum Structure from Cores to Clumps across the Galactic Disk

First Author: Wallace, Jennifer
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00195.L
BibCode: 2026ApJ...998..302W

Investigating the multiscale fragmentation of dense clumps into compact cores is essential for understanding the processes that govern the initial distribution of mass in stellar clusters and how high-mass stars (>8 M_⊙) form. We present a catalog of the hierarchical continuum structure from 904 clumps observed in the ALMAGAL program, a high-resolution (0 .″ 15─0 .″ 8) 1.38 mm Atacama Large Millimeter/submillimeter Array large program targeting dense clumps capable of high-mass star formation throughout the Galactic disk. We use astrodendro, a dendrogram-based algorithm, on a uniform linear resolution (2000 au) version of the data to extract 5160 continuum structures with effective radii spanning 800─42000 au and estimated masses between 0.05─670 M_⊙. With our large sample, we statistically examine differences in clump properties for regions with varying levels of hierarchical complexity. We find that clumps exhibiting the richest hierarchical morphology have distributions with higher dust temperatures, surface densities, luminosity-to-mass (L/M) ratios, and most massive core masses, indicating that these regions tend to be at later evolutionary stages. We find a positive correlation between the mass of cores from the ALMAGAL core catalog and the surface density of their surrounding structures identified in this work. However, this correlation is weaker for cores in more evolved clumps, where lower-mass cores can be found at higher local surface densities. This could indicate that some cores accrete mass less efficiently from the intraclump reservoir than others, despite the total available mass increasing over time, a scenario that is congruent with a clump-fed core accretion model.

Characterizing the physical and chemical properties of the Class I protostellar system Oph-IRS 44: Binarity, infalling streamers, and accretion shocks

First Author: Artur de la Villarmois, E.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2022.1.00209.S, 2019.1.01792.S
BibCode: 2026A&A...706A.256A

Context. In the low-mass star formation process, theoretical models predict that material from the infalling envelope could be shocked as it encounters the outer regions of the disk. This is followed by an increase in the dust temperature and sublimation, into the gas phase, of molecular species that will otherwise remain locked on dust grains. Although accretion shocks are predicted by theoretical models, only a few protostars show evidence of these shocks at the disk-envelope interface, and the main formation path of shocked-related species is still unclear. They can be formed entirely on dust surfaces and then sublimated, or through reactions in the gas phase, or a combination of both. Aims. The goal of this work is to assess the chemistry associated with accretion shocks and the formation path of molecules that are usually associated with these dense and warm regions. Methods. We present new observations of IRS 44, a Class I source with a resolved disk that has previously been associated with accretion shocks, taken at high angular resolution (0_⋅^''1, corresponding to 14 au) with the Atacama Large Millimeter/submillimeter Array (ALMA). We observe three different spectral settings in bands 6 and 7, targeting multiple molecular transitions of CO, H₂CO, and simple sulfur-bearing species (such as CS, SO, SO₂, H₂S, OCS, and H₂CS). Results. In continuum emission, the binary nature of IRS 44 is observed for the first time at sub-millimeter wavelengths and the emission agrees with the optical and infrared counterparts. Infalling signatures are seen for the CO 2─1 line and the emission peaks at the edges of the continuum emission around IRS 44 B, the same region where bright SO and SO₂ emission is seen. Weak CS and H₂CO emission is observed, while OCS, H₂S, and H₂CS transitions are not detected. Conclusions. IRS 44 B seems to be more embedded than IRS 44 A, indicating a non-coeval formation scenario or the rejuvenation of source B due to late infall. CO 2─1 emission is tracing the outflow component at large scales, infalling envelope material at intermediate scales, and two infalling streamer candidates are identified at disk scales. Infalling streamers might produce accretion shocks when they encounter the outer regions of the infalling-rotating envelope. These shocks heat the dust and efficiently release S-bearing species (such as H₂S, SO, and SO₂), as well as promoting a lukewarm chemistry (~200 K) in the gas phase. With the majority of carbon locked in CO, there is little free C available to form CS and H₂CS in the gas, leaving an oxygen-rich environment. The high column densities of SO and SO₂ might therefore be a consequence of two processes: direct thermal desorption from dust grains and gas-phase formation due to the availability of O and S. IRS 44 is an ideal candidate with which to study the chemical consequences of accretion shocks and the dynamical connections between the envelope and the disk, through infalling streamers.

δ Circini: A massive hierarchical triple system with an eclipsing binary

First Author: Svrckova, J.
Instruments: FEROS, GRAVITY, HARPS, PIONIER
ProgramIDs: 089.C-0211, 189.C-0644, 093.C-0503, 098.D-0706, 099.D-0777, 596.D-0495, 5100.D-0721, 182.D-0356, 185.D-0056, 178.D-0361, 109.23HT
BibCode: 2026A&A...705A..99S

δ Circini is known to be a massive multiple system containing a 3.9 d inner eclipsing binary in a slightly elliptical orbit exhibiting slow apsidal motion and a distant tertiary with a probable period of 1644 d. All three components of the system are O- or B-type stars. We carried out a comprehensive study of the system, based on light curves from TESS and other instruments, a new series of echelle spectra, older spectra from the ESO archive, and several VLTI interferometric observations. Due to the large amount of different types of data covering both orbits in the system, we obtained a more precise value of the long orbital period (1603.24 ± 0.19 d) and fully determined all other orbital parameters. Although both orbits are eccentric, their period ratio is large enough for the system to be dynamically stable. The inner and outer orbits are in the same plane, which means that no Kozai-Lidov mechanism is acting in the system. Assuming solar metallicity in our MESA models, we found ages of (4.4 ± 0.1), (4.7 ± 0.2), and (3.8 ± 1.3) Myr for the primary, the secondary, and the tertiary, respectively. Our evolutionary scenario predicts that the inner eclipsing binary will merge within approximately 1.7 Myr and eventually evolve into a black hole. The distance to the system, estimated from the angular size of the outer orbit is (809.9 ± 1.8) pc, which implies that δ Cir might be located close to the centre of a stellar population ASCC 79, a subgroup of the young Circinus complex. With a total mass of (53.04 ± 0.29) M_⊙, δ Cir can contribute a significant fraction of the total mass of the population.

On the dusty proximate damped Lyman-α system toward Q 2310−3358 at z = 2.40

First Author: Han, S.
Instruments: XSHOOTER
ProgramIDs: 113.268S
BibCode: 2026A&A...705A.123H

Quasar absorption systems not only affect the way quasars are selected, but also serve as key probes of galaxies, providing insight into their chemical evolution and interstellar medium (ISM). Recently, a method based on Gaia astrometric measurements has aided the selection of quasars reddened by dust hitherto overlooked. We conducted a spectroscopic study using VLT/X-Shooter on one such dust-reddened quasar, Q 2310─3358. This quasar, at z = 2.3909 ± 0.0022, is associated with a damped Lyman-α absorber (DLA) at nearly the same redshift 2.4007 ± 0.0003, with a neutral hydrogen column density of log N(H I) = 21.214 ± 0.003. The DLA is very metal-rich (close to solar metallicity after correction for depletion on dust grains). Its properties align with the metal-to-dust ratio and the mass-metallicity relation established in previous large samples of DLAs. Surprisingly, given its proximity to the quasar in redshift, the absorber has strong cold gas characteristics, including C I and H₂. Based on the derived kinetic temperature of 71₋₁₅⁺²⁸ 71 − 15 + 28 K, we infer the presence of a strong UV radiation field, which in turn suggests that the quasar and the DLA are in close proximity, i.e., part of the same galaxy and not just different objects in the same overdensity of galaxies. We used the line ratios of the C I fine-structure lines to constrain the density of the cold gas, yielding n_H ∼ 10³ cm⁻³. Our analysis extends the understanding of z_abs ≍ z_em absorption line systems and provides valuable constraints on the interplay between dust, metals, and neutral gas in the ISM of early galaxies.

Extreme Neutral Outflow in a Non-active Galactic Nucleus Quiescent Galaxy at z ∼ 1.3

First Author: Sun, Yang
Instruments: MUSE
ProgramIDs: 1101.A-0127, 096.A-0045, 095.A-0010, 094.A-0289
BibCode: 2026ApJ...997..140S

We report the discovery of a substantial sodium doublet (Na D λλ5890, 5896)—traced neutral outflow in the quiescent galaxy JADES-GS-206183 at z = 1.317. Its JWST/NIRSpec-Microshutter Array spectrum shows a deep, blueshifted Na D absorption, revealing a neutral outflow with vout=828−49+79kms−1 and a mass outflow rate of log(Ṁout/M⊙yr−1)=2.40−0.16+0.11 . This outflow rate exceeds that of any neutral outflows identified beyond z ∼ 1 by the same line and is comparable with those in local galaxies with intensive star formation (SF) or luminous active galactic nuclei (AGN). JADES-GS-206183 is also a peculiar quiescent galaxy with a spiral+bar morphology, high dust attenuation (A_V = 2.27 ± 0.23 mag). Paschen α (Paα) emission from the FRESCO NIRCam grism confirms its low star formation rate (SFR_Paα = 10.78 ± 0.55 M_⊙ yr⁻¹), placing it 0.5 dex below the main sequence ( log(sSFRyr−1)=−10.2 ). Despite the systematics introduced by different SF history priors, the spectral energy distribution modeling, combining Hubble Space Telescope-to-NIRCam photometry with the Very Large Telescope/MUSE spectrum, suggests that JADES-GS-206183 experienced an older episode of SF 0.5─2 Gyr ago and a possible rejuvenation within the recent ∼10 Myr. Moreover, rest-frame optical lines indicate that the current AGN activity of JADES-GS-206183, if present, is also weak. Even though we tentatively detect a broad component of the Hα line, it likely traces an ionized outflow rather than an AGN. The results demonstrate that the Na D outflow in JADES-GS-206183 is highly unlikely to be driven by current SF or nuclear activity. Instead, it may represent a long-lasting fossil outflow from past AGN activity, potentially cotriggered with the early phase of rejuvenation.

The Galaxy Activity, Torus, and Outflow Survey (GATOS): X. Molecular gas clumpiness under the influence of AGN

First Author: Esposito, Federico
Instruments: ALMA_Band_7
ProgramIDs: 2017.1.00082.S, 2018.1.00113.S
BibCode: 2026A&A...705A..33E

The distribution of molecular gas on small scales regulates star formation and the growth of supermassive black holes in galaxy centers. Yet, the role of active galactic nuclei (AGN) feedback in shaping this distribution remains poorly constrained. We investigate how AGNs influence the small-scale structure of molecular gas in galaxy centers by measuring the clumpiness of CO(3 − 2) emission observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in the nuclear regions (50 − 200 pc from the AGNs) of 16 nearby Seyfert galaxies from the Galaxy Activity, Torus, and Outflow Survey (GATOS). To quantify clumpiness we applied three different methods: (1) the median of the pixel-by-pixel contrast between the original and smoothed maps; (2) the ratio of the total excess flux to the total flux, after subtracting the background smoothed emission; and (3) the fraction of total flux coming from clumpy regions, interpreted as the mass fraction in clumps. We find a negative correlation between molecular gas clumpiness and AGN X-ray luminosity (L_X), suggesting that higher AGN activity is associated with smoother gas distributions. All methods reveal a turnover in this relation around L_X = 10⁴² erg s⁻¹, possibly indicating a threshold above which AGN feedback becomes efficient at dispersing dense molecular structures and suppressing future star formation. Our findings provide new observational evidence that AGN feedback can smooth out dense gas structures in galaxy centers.

Probing jet base emission of M87* with the 2021 Event Horizon Telescope observations

First Author: Saurabh
Instruments: ALMA_Band_6
ProgramIDs: 2017.1.00841.V, 2019.1.01797.V
BibCode: 2026A&A...706A..27S

We investigate the presence and spatial characteristics of the jet base emission in M87* at 230 GHz, enabled by the significantly enhanced (u,v) coverage in the 2021 Event Horizon Telescope (EHT) observations. The integration of the 12−m Kitt Peak Telescope (USA) and NOEMA (France) stations into the array introduces two critical intermediate-length baselines to SMT (USA) and IRAM 30−m (Spain), providing sensitivity to emission structures at spatial scales of ∼250 μas and ∼2500 μas (∼ 0.02 pc and ∼ 0.02 pc). Without these new baselines, previous EHT observations of the source in 2017 and 2018 lacked the capability to constrain emission on large scales, where a "missing flux" of order ∼1 Jy is expected to reside. To probe these scales, we analyzed closure phases─robust against station-based gain calibration errors─and model the jet base emission using a simple Gaussian component offset from the compact ring emission at spatial separations > 100 μas. Our analysis revealed a Gaussian feature centered at (∆RA ≍ 320 μas, ∆Dec. ≍ 60 μ as), projected separation of ≍ 5500 AU, with an estimated flux density of only ∼60 mJy, implying that most of the missing flux identified in previous EHT studies had to originate from different, larger scales. Brighter emission at the relevant spatial scales is firmly ruled out, and the data do not favor more complex models. This component aligns with the inferred position of the large-scale jet and is therefore physically consistent with the emission of the jet base. While our findings point to detectable jet base emission at 230 GHz, the limited coverage provided by only two intermediate baselines limits our ability to robustly reconstruct its morphology. Consequently, we treated the recovered Gaussian as an upper limit on the jet base flux density. Future EHT observations with expanded intermediate baseline coverage will be essential to constrain the structure and nature of this component with higher precision.

ALMA and JWST Imaging of z > 6 Quasars: No Spatial Position Offset Observed between Quasars and Their Host Galaxies

First Author: Wilde, Aurora
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00908.S, 2018.1.01188.S, 2019.1.00672.S, 2019.1.01025.S, 2021.1.00934.S
BibCode: 2026ApJ...996....8W

We present a study determining the spatial offset between the position of the supermassive black hole (as traced through their broad line regions) and the host galaxy in six z > 6 quasars. We determined the host galaxy's position from ≲ 0.″10 (≲600 pc) resolution Atacama Large Millimeter/submillimeter Array (ALMA) [C II] 158 μm and corresponding dust continuum imaging. We determined the quasar's position from ≲400 pc resolution James Webb Space Telescope Near-Infrared Camera (JWST NIRCam) imaging. We estimated the observational uncertainties on the quasar's position using astrometric data from the Global Astrometric Interferometer for Astrophysics of field stars within the NIRCam images. We find that all six quasars are found within the central ∼400 pc of their host galaxy dust continuum and [C II] emission. Apparent offsets seen in rest-frame optical JWST observations are not detected in our ALMA data, suggesting they likely result from dust obscuration rather than a true physical separation between the SMBH and its host galaxy. Kinematic modeling of these data further reveals that none of the galaxies show evidence for recent merger activity, and most of the galaxies can be accurately modeled using a simple disk model. The lack of an offset supports theoretical models that predict that positional offset within these galaxies is either short-lived or intrinsically rare.

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Orbital Motions of Binaries in Orion South

Massive dusty multiphase outflow in local merger shows no sign of slowing on kiloparsec scales

Bar-driven Shocks in NGC 1365 Revealed by the Most Luminous Extragalactic Class I Methanol Maser

Digging into the Chemical Complexity in the Outer Galaxy: A Hot Molecular Core in Sh 2-283

Older Ages for 23 Pre-main Sequence Stars in Upper Scorpius Using Dynamical-mass-constrained Stellar Evolutionary Models

Upper Limit on HF(1─0) Absorption in a Dusty Star-forming Galaxy at z = 6: Constraints on Early Fluorine Enrichment

Spatially resolved star formation relations in local luminous infrared galaxies along the complete merger sequence

Direct Spectroscopic Confirmation of the Young Embedded Protoplanet WISPIT 2c

The Chemical Diversity of Giant-planet Nurseries as Revealed by ALMA

A near-infrared and optical study of NGC 5822: an open cluster hosting barium-stars and lithium-enriched giant stars

A Search for Late-type Brown Dwarfs in the Euclid Quick Data Release 1

Astrometric and Spectroscopic Analysis of IC 2714: An Open Cluster Hosting a Lithium-rich Giant

Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES+ observations

Dissecting the dust distribution and polarization around two B213 young stellar objects with ALMA

Discovery of Multiple Ultra-broad-velocity Molecular Features Associated with the W44 Molecular Cloud

Young system development in a cometary globule: An investigation into the eccentric disk around AT Pyx^* in terms of planet formation and interaction with its surrounding environment

CH₃OH and HCN in Interstellar Comet 3I/ATLAS Mapped with the ALMA Atacama Compact Array: Distinct Outgassing Behaviors and a Remarkably High CH₃OH/HCN Production Rate Ratio

Detailed lens modeling and kinematics of the submillimeter galaxy G09v1.97: An analysis of CO, H₂O, H₂O⁺, and dust continuum emission

Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES⁺ observations

ALMA Polarization Study of the Magnetic Fields in Two Massive Clumps in the 20 km s⁻¹ Cloud of the Central Molecular Zone