G4S_2.0 is a new project funded by the Italian Space Agency which aims to perform measurements in the field of Fundamental Physics with two satellites, DORESA and MILENA, of the Galileo-FOC constellation. These satellites are characterized by the high eccentricity of their orbits and the accuracy of their atomic clocks. For these characteristics, they have recently been used to improve a previous measurement of gravitational redshift (GRS) by Gravity Probe-A in 1980 ([1]). GRS, which is a local position-invariance test, is only one of the predictions of General Relativity (GR) that can be tested with the Galileo constellation. In particular, the G4S_2.0 project aims to provide a new measurement of GRS and to measure relativistic precessions of the elliptical orbits. These results will place new constraints on possible alternative theories of gravitation, both metric and non-metric in their structure. Furthermore, constraints on the presence of Dark Matter in our Galaxy can be placed by analyzing the data of the constellation's atomic clocks. In this framework a fundamental point is obtaining a satellite orbit solution precise as far as possible. For this purpose, we focus firstly on the precise orbit determination and on a dynamic model for the non-conservative forces acting on these satellites. In particular, the model manages the perturbing effects produced by the direct solar radiation pressure (the major perturbation), the Earth’s infrared radiation and the Earth-albedo. The results of G4S_2.0 project will extend the number of tests of Einstein’s Theory of GR that can be achieved with Galileo satellites. [1] Vessot R.F.C. et al., (1980) Test of relativistic gravitation with a spaceborne hydrogen maser. Phys Rev Lett 45(26):2081–2084. https://doi. org/ 10. 1103/ Phys. Rev. Lett. 45. 2081. 

The currently hierarchical model of the formation of the Milky Way is based on the idea that a series of accretion and merging events led to its assemble. These accretion events may leave their imprint in the form of structures such as stellar streams, shells or clouds, which appear as overdensities with respect to the underlying halo distribution. Thus, finding new overdensities idates is crucial to properly infer our galaxy's formation history. RR Lyrae (RRL) stars have been used to find or trace the shapes of many Milky Way halo overdensities. This is because RRL are sufficiently rare to not randomly form in pairs outside of stellar structures. However, we required a kinematic analysis on RRL to relate them to the same structure. In our work, we had been analyzing the orbits and special distribution of known overdensities and new idates. Our sample of RRL contains their 3D spatially positions, proper motions, radial velocities, and in some cases chemical composition. In this talk, we will be sharing our kinematic analysis of this sample. We will also discuss the importance of finding new overdensities and how increasingly larger databases, such as afforded by Gaia, make it necessary to implement improved data analysis techniques in order to more proper and efficient analysis. Finally, we will discuss the efficiency of clustering algorithms, such as DBSCAN, in the classification of new idates of stellar overdensities, by analyzing the effectiveness to recognize known overdensities, such as Virgo Overdensity. 

Radio-Loud (RL/jetted) AGNs are among the brightest sources at all wavelengths and are usually associated with the densest regions of the Universe. Their relativistic jets can affect both the SMBH growth and the surrounding IGM and have been observed extending up to Mega-parsec scale.

After 20 years from the detection of the first extended kilo-parsec extragalactic jet in the X-rays, the mechanism responsible for their high-energy emission at these scales is still under debate.

At the same time, it was recently found that the cosmological evolution of the jetted AGN population significantly differs when observed in the X-ray or the radio band. Their X-ray space density peaks at much earlier times (z~4) when compared to their radio one (z~2), which would imply a different redshif evolution of the typical X-ray luminosities with respect to the radio ones.

In this talk I will show how the Inverse Compton interaction between the CMB photons and the electrons within relativistic jets (IC/CMB) can nicely solve both these problems. Our results are based on statistical studies performed on the largest well-defined samples available to date (up to z~5) and the detailed study of the most distant X-ray jet resolved to date (z=6.1).

Finally, I will also present our efforts to expand current samples at even higher redshift, where the effect of the CMB is stronger. By exploiting the most recent radio surveys, in less than one year we were able to discover three new RL AGNs at z>6, where only four were known before.

We present a new model for the evolution of spatially-resolved gas-phase metallicities in galaxies from first principles. We show that metallicities depend on four ratios that collectively describe the metal equilibration time-scale, production, transport, consumption, and loss. When normalized by metal diffusion, metallicity gradients are governed by the competition between radial advection, metal production, and accretion of metal-poor gas from the cosmic web. The model naturally explains the varying gradients measured in local spirals, local dwarfs, and high-redshift star-forming galaxies. We use the model to study the cosmic evolution of gradients across redshift, showing that the gradient in Milky Way-like galaxies has steepened over time, in good agreement with both observations and simulations. Simultaneously reproducing the observed mass-metallicity and massmetallicity gradient relations in the local Universe from the model also shows that galaxies transition from the advection-dominated to the accretion-dominated regime as they increase in mass. The same transition also occurs in galaxies from high to low redshifts, which mirrors the transition from gravity-driven to star formation feedback-driven turbulence. The shape of metallicity-based galaxy scaling relations is governed by the metal enrichment of outflows. Lastly, we show that the model also explains the observed relationship between metallicity gradients and galaxy kinematics at high redshift, and provides direct predictions for galactic chemical evolution that can be tested against future observations. 

Stars comprising the Milky Way's stellar halo safeguard important chemo-dynamical information that enables the reconstruction of the mass assembly history of the Galaxy. Of particular importance are the halo populations in the innermost regions of the Milky Way, as they likely retain pivotal information that may help decode the early stages of the formation of the Galaxy, but however have so far been concealed due to the limitations in observing such regions due to high stellar density and dust extinction. In this talk I will present results from two independent studies aimed at tackling two open questions in Galactic archaeology: "What is the Milky Way's mass assembly history?"; and "How much do globular clusters (GC) contribute to the total stellar halo mass budget?". First, I will provide evidence for the discovery of a new metal-poor substructure that displays chemo-dynamic signatures of accreted populations located within the heart of the Galaxy. Given the properties of this newly identified substructure (dubbed "Heracles"), we conjecture that it is the remnant of an accretion event that occurred in the early life of the Galaxy, which constituted a major building block of the Milky Way halo, and played a major role in the formation of the Milky Way. Following, I will present results on a study focused on assessing the contribution of dissolved and/or evaporated GC stars to the Galactic stellar halo. Using a density modelling procedure, I will show results that suggest there is a much higher contribution of dissolved/evaporated GC stars in the inner regions of the Galaxy when compared to the outer regions. The results presented in this talk help shed light on the nature of Galactic stellar halo populations and the mass assembly history of the Galaxy.

Stellar activity poses a severe limitation to the search and characterisation of small exoplanets with the radial velocity method. This is particularly important for M dwarfs, as they are crucial targets for both ground-based instruments (e.g., SPIRou, NIRPS, CRIRES) as well as space-based missions (e.g., JWST, ARIEL), but can manifest high activity levels over long time-scales. Efficient activity filtering techniques are therefore necessary to disentangle genuine planetary signatures and improve the detectability. In this context, and knowing from previous studies that different spectral lines are affected differently by magnetic activity, we developed a new mitigating technique based on a randomised selection of lines to use in Least-Square Deconvolution (LSD). We benchmarked the analysis on optical spectropolarimetric time series of the active M dwarf EV Lac collected with ESPaDOnS at CHFT, obtaining a reduction of the radial velocity dispersion by at least 50- 60%. A similar and consistent improvement was also found when targeting stars of analogous (AD Leo) and lower (DS Leo) activity levels. Finally, we injected synthetic planets with semi-amplitudes between 60 and 120 m/s (i.e. 0.3-0.6 MJup) in our data sets containing moderate (20 m/s) and high (200 m/s) activity levels and we retrieved reasonably unaltered planetary signals, indicating that our technique does not suppress these signals substantially. 

Massive stars play crucial roles in determining the physical and chemical evolution of galaxies. They shape their environment from early in their protostellar phase when they blast the surrounding with powerful jets, up until their violent deaths in the form of supernova. However, they form deeply embedded in their parental clouds, making it challenging to directly observe these stars and immediate environments. Notwithstanding, their massive outflows can extend several parsecs and since accretion and ejection processes are intrinsically related, they can provide crucial information about the processes governing massive star formation. In this talk, I will present the IRAS 18264-1152 high-mass star-forming complex and reveal the jets through NIR spectro-imaging. We observe the molecular hydrogen (H2) NIR jets in the K-band (1.9-2.5µm) obtained with the integral field units VLT/SINFONI and VLT/KMOS. We compare the geometry of the NIR outflows with that of the associated molecular outflow, probed by CO(2-1) emission mapped with the SMA. The spectro-imaging analysis focuses on the H2 jets, for which we derived visual extinction, temperature, column density, area, and mass. The intensity, velocity, and excitation maps based on H2 emission strongly support the existence of a protostellar cluster in this region, with at least two (but up to four) different large-scale outflows, found through the NIR and radio observations. This multi-wavelength comparison also allows us to derive a stellar density of 4000 stars pc-3 showing that relatively low number density region can harbour massive protostars. In conclusion, our study reveals the presence of several outflows driven by young sources from a forming cluster of young massive stars. Moreover, the derived stellar number density together with the geometry of the outflows suggest that massive stars can form in a relatively ordered manner in this cluster.

While numerous exoplanets have now been uncovered in stellar binaries, the impact of companion stars on planet formation and evolution is still not understood. In this talk, I will present results of population trends seen among the known sample of planets in multiple star systems, which allows us to investigate the effects of stellar binarity on the resulting planetary architectures. In particular, observations of stars hosting high-mass close-in giant planets and brown dwarfs find an excess of binary companions on few hundred AU separations, and different planet demographics for these systems, suggesting that such binaries may provide favourable conditions for the formation of the observed inner companions. I will show results from simulations of self-gravitating protoplanetary disks adapted to binary-star environments, which show that certain binary configurations may trigger gravitational fragmentation and lead to the formation of giant planets in otherwise stable disks.

Brown dwarfs (BDs) lie in the substellar mass regime, and are a bridge between stars and planets, thus providing a unique window into the unknowns of their formation processes. The dominant mechanism behind the formation of BDs is still not fully constrained. In fact, BD formation is expected to be affected by the environment in which they are born, in particular, an environment with high stellar densities and/or large number of massive stars would increase the efficiency of BD production compared to stars. In order to test these hypotheses, we are studying the low-mass population of three massive young clusters with extreme environmental properties compared with nearby star-forming regions. One of these clusters is NGC 2244 (d=1.5 kpc), which hosts a large number of OB stars and presents a low stellar density. We have built a robust sample of cluster members using deep photometry, astrometry and multi-object spectroscopy (VIMOS and KMOS/VLT), resulting in the first spectroscopically confirmed BDs beyond 1 kpc. In this talk, I will present our newly developed method for spectroscopic analysis of cool dwarf spectra in the NIR, implementing machine learning models to efficiently separate young members from field contaminants, that will be of special interest for upcoming multi-object facilities such as NIRSPEC and NIRISS/JWST and MOONS/VLT. Furthermore, I will present our results on the BD population in NGC 2244 and compare them with the other massive clusters in our sample, as well as with nearby star-forming regions.

The Galactic Center harbors a peculiar population of young stars some distributed in a clockwise rotating disk. In this talk I will present the largest spectroscopic survey of the Nuclear Star Cluster using over 600 hours of ESO's SINFONI instrument. The observations were carried out over the last two decades and now cover roughly 25 arc-seconds squared of the Galactic Center. This is a substantial increase in coverage compared to previous works. The analysis of the spectra has led to the spectroscopic classification of over 2800 stars. We identified around 90 new young stars increasing the total number of known young stars by almost a factor two to ~200. Furthermore, I will show that these young stars are not isotropically distributed, but instead reside in a system consisting of a central warped clockwise disk and several streamers/ streams of young stars at larger radii. Lastly, I will discuss the implications of this result for star formation in the Galactic Center, where I will argue that the young stars formed after the collision and subsequent accretion of two giant molecular clouds about 6 mega years ago. 

The huge improvements in the precision of the published data in Gaia EDR3, particularly for parallaxes and proper motions, has given a push to the detection of new open clusters in the Milky Way. In this talk, I will revise our methodology to search for open clusters, and how it has been adapted to a Big Data environment to analyse hundreds of millions of stars looking for relations and patterns among them. The application of the method to Gaia EDR3 has resulted in the discovery of 664 new open clusters, which, added to the 646 found in our previous searches in Gaia DR2, represent about 50% of the known open cluster population. I will also revise how this updated open cluster catalogue, with estimated astrophysical parameters, can provide insights about the structure and evolution of our Galaxy, particularly focusing on the spiral arms

Cool giant and supergiant stars are among the largest and most luminous stars in the Universe and, therefore, dominate the integrated light of their host galaxies. These stars were extensively studied during last few decades, however their relevant properties like photometric variability and mass loss are still poorly constrained. Understanding of these properties is crucial in the context of a broad range of astrophysical questions including chemical enrichment of the Universe, supernova progenitors, and the extragalactic distance scale. The atmospheres of evolved stars are characterized by complex dynamics due to different interacting processes, such as convection, pulsation, formation of molecules and dust, and the development of mass loss. These dynamical processes impact the formation of spectral lines producing their asymmetries and Doppler shifts. Thus, by studying the line-profile variations on spatial and temporal scales it is possible to reconstruct atmospheric motions in stars and link them to the photometric variability and mass loss. The tomographic method, which is based on the cross-sectioning through the stellar atmosphere and recovering the velocity field for each atmospheric slice, is an ideal technique for this purpose. In this colloquium, I will present the tomographic method and its application to spectroscopic and spectro-interferometric observations of giant and supergiant stars as well as to state-of-the-art three-dimensional numerical simulations to constrain their atmospheric motions on spatial and temporal scales and better understand respective mechanisms responsible for their photometric variability and mass loss.

Majority of classical Cepheids are binary stars, yet the contribution of companions' light to the total brightness of the system has been assumed negligible and lacked thorough, quantitative evaluation. I present an extensive study of synthetic populations of binary Cepheids, that aims to characterize Cepheids' companions (e.g. masses, evolutionary and spectral types), quantify their contribution to the brightness and color of Cepheid binaries, and assess the relevance of input parameters on the results. Synthetic populations are free from the selection and completeness biases, while the percentage of Cepheid binaries is controlled by the binarity parameter. With this tool I successfully reproduce recent theoretical and empirical results: the percentage of binary Cepheids with main sequence (MS) companions, the contrast-mass ratio relation for binary Cepheids with MS companions, the manifestation of binary Cepheids with evolved, giant companions as outlier data points above the period-luminosity relation. Next, I use the synthetic populations to estimate, for the first time, the percentage of binary Cepheids in the Large Magellanic Cloud, and quantify the effect of binarity on the slope and zero point of multiband period-luminosity relations. Finally, I present a promising method of detecting binary Cepheids on color-color diagrams, provided multi-epoch, high quality, multi-band data. Large volumes of such data are anticipated from Vera C. Rubin Observatory, presenting an exciting opportunity for discovery of binary Cepheids on a large-scale.

The Fornax galaxy cluster provides an unparalleled opportunity of investigating galaxy formation and evolution in a dense environment in great detail. Although the Fornax cluster seems relaxed, various studies have shown that the Fornax cluster still is accreting various sub-groups. Previous photometric studies of the central massive galaxy NGC1399 revealed an excess of globular clusters (GCs), suggesting accretion of GCs from nearby, interacting major galaxies like NGC 1404. To kinematically characterize the Fornax cluster's intra-cluster population and understand the assembly of the outer halos of cluster galaxies, we have analyzed the VLT/VIMOS spectroscopic survey of the Fornax cluster covering half of the cluster virial radius (~300 kpc). Combined with previous spectroscopic measurements, this leads to the most extensive catalogue of radial velocity measurements with a total of 2341 confirmed GCs in Fornax. Our analysis of this unprecedented dataset provides the kinematical characterization of the Fornax cluster's intra-cluster component. We found that metal-rich GCs are concentrated around the major galaxies, while metal-poor GCs are kinematically irregular and extensively spread throughout the cluster's core region. About 30% of the GCs contribute to the intracluster population. With the final goal to understand the mass assembly of the Fornax cluster and its member galaxies, in this talk, I will present the kinematics of GCs in the core of the cluster, and ongoing dynamical mass-modelling results obtained from this dataset. I will discuss possible kinematical interaction signatures between NGC1399 and the major galaxies of the Fornax cluster. 

An important fraction of quasars are red at optical wavelengths, indicating (in the vast majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In recent work by our group, we have shown fundamental differences in the radio properties of SDSS optically selected red quasars, which cannot be explained with a simple viewing angle hypothesis (Klindt et al. 2019, Fawcett et al. 2020, Rosario et al. 2020, Rosario et al. 2021). In our latest work, we use VLT/X-shooter spectroscopy of a sample of red and typical quasars to gain insight into these differences. We confirm that dust reddening is the main cause of the red colours and explore the emission line properties of our sample. We confront our spectra against accretion disc models and confirm that red quasars are powered by standard thin-disc accretion, finding tentative evidence that red quasars have higher Eddington ratios for any given black hole mass. These results suggest that dusty winds could be driving the fundamental differences in red quasars, and so they may represent an important phase in galaxy evolution. Using DESI spectra, we can now push to more extinguished, lower luminosity systems, which will test whether these results extend to more extreme reddened systems. 

One of the exciting results of the last years concerning the study of the large-scale structure is the discovery of long (3-5 Mpc) bridges of radio emission connecting pairs of interacting clusters. This is the first direct evidence of the existence of particle acceleration and magnetic field amplification mechanisms outside galaxy clusters. Non-thermal components spread over such vast extents probe the dynamics of large-scale structures and the mechanisms of energy dissipation therein. In my talk, I will discuss recent results on radio bridges, showing how their observation represents a step forward in the search of the radio signature of the magnetized cosmic web. 

Quasi-Periodic Eruptions (QPEs) are high-amplitude bursts of X-ray radiation recurring every few hours and provide a new channel to study how massive black holes are activated in low-mass galaxies. Previously, only two such sources were known, classified as hosting an actively accreting black hole. I will present the detection of QPEs in two further galaxies, obtained with a blind and systematic search during the first year of operations of the eROSITA X-ray telescope (Arcodia et al., Nature 2021). The optical spectra of these galaxies show no signature of black hole activity, indicating that a pre-existing accretion flow typical of active nuclei is not required to trigger these events. I will give a state-of-the-art overview of QPEs' multi-wavelength observational properties and possible origin scenarios. What we currently suggest is that QPEs might be driven by the presence of one (or more) orbiting body (-ies) with stellar mass. This could make QPEs a viable idate for the electromagnetic counterparts of the so-called extreme mass-ratio inspirals, with considerable implications for the future of multi-messenger astrophysics and cosmology.

The formation of high-mass stars has seen some significant progress over the past years. Still, being deeply embedded in their natal envelope, a definitive observational sequence for their formation is yet to be obtained. Most main sequence massive stars (~70%) belong to short-period binaries, a fact that does not reflect the binary parameters measured among populations of newly born massive stars. To bridge the gap between these two regimes, we need to obtain strong constrains on the origin of the pairing mechanism and the birth orbital properties. Different scenarios have been proposed to produce close binaries, such as the migration, in which massive binaries are originally formed at large separations and then harden on a time-scale of ~2 Myr. A strong test for this scenario is the presence of a significant number of relatively massive companions at separations corresponding to the expected size of the accretion disk. Being one of the youngest cluster in our Galaxy, M17 is an unprecedented laboratory where (proto)binaries can be caught during or immediately after their formation phase. In my talk, I will describe how optical interferometry (GRAVITY) and high-angular resolution techniques (NACO) are of great importance in characterizing multiplicity at birth. From the interferometric model fitting of visibility amplitudes and closure phases, I will present some of my latest exciting results, including two important concepts: the multiplicity and companion fraction. These results will be compared to other recent studies. Finally, I will discuss the connection with the current star formation theories and how the advent of future VLTI instrumentation will bring another piece to the puzzle.

I will present an overview of the Quasar Feedback Survey (QFeedS) and will illustrate its powerful capabilities to establish the role of rapidly growing supermassive black holes (i.e., quasars) in galaxy evolution. Using spatially-resolved ionized gas and stellar kinematic measurements from MUSE data, molecular gas kinematics from ALMA data, and high-quality imaging from the VLA, we are measuring in exquisite detail how z<0.2 quasars interact with the host galaxy’s interstellar medium (ISM). By combining these data, we can infer the feedback effects on the host galaxy: 1) there are clear signatures of the impact of radio jet-ISM interactions in both the ionized and molecular phases; 2) we observe outflowing, dense turbulent gas, perpendicular to the jet axis, extending to galactic scales; 3) we observe evidence for jet-induced feedback on the stellar properties. Recent simulations of jet-ISM interactions, qualitatively agree with our observations; specifically, as inclined, low power jets move through the galaxy, they strongly interact with the ISM, causing highly turbulent material to be stripped, which then escapes above and below the galaxy disk. The overall impact is to both remove gas from the host galaxy (globally suppressing star formation) and to compress the gas (locally inducing star formation). Through my analysis, I present a discussion of how such jet-induced feedback could be an important, previously underappreciated, feedback mechanism for bolometrically luminous 'radio quiet' quasars.

New planetary systems are made from dust and gas in the rotating disks around young stars. High-resolution observations of these planet-forming disks with the Atacama Large Millimeter Array (ALMA) can be used to learn about the planet-formation process. In particular, ALMA can trace the composition of the gas available to be accreted by planets. In this talk, I will show recent molecular line observations towards two well-studied warm planet-forming disks: HD100546 and IRS48. These disks show evidence for ongoing planetformation due to the presence of rings and asymmetries in the millimetre dust disk. The molecular emissions are linked to these dust structures. These data include first detections of the molecules NO, SO2 and CH3OCH3 in protoplanetary disks. This rich observable chemistry is due to ice sublimation and the link between the molecules and the dust structures shows that these dust traps are also ice traps. The array of detected molecules can be used to learn about the physical and chemical conditions in the disk experienced by forming planets. We determine the elemental C/O ratio in the disk using the simple molecules (SO, CS etc), and this provides a direct connection to the observed exoplanet population. On the other hand, the more complex molecules (CH3OH, CH3OCH3, etc.) shed light on the importance of inheritance from earlier stages of the star formation process. The detection of these complex and potentially prebiotic molecules in planet-forming disks provides links to how life originated in our solar system.

Most exoplanet surveys have so far focused on stars not larger than the Sun, and about 90% of the 4500 known exoplanets lie closer to their stars than the Earth is to the Sun. This strong observational bias has recently started being complemented by direct imaging, a technique that -contrary to transits and radial velocities- is preferentially sensitive to young giant planets in wide orbits. Although giant planets have been shown to be increasingly common around more massive star, the occurrence frequency, according to radial velocity studies, has a turnover at about 2 M_sun and goes down to zero at M>3 M_sun. This is in line with theoretical expectations from the core accretion model: due to a more rapid dispersal of the protoplanetary disk around heavier stars, giant planets around intermediate and massive stars should simply not exist. To clarify if this shortage is real or if it is rather the result of an observational bias, we initiated the direct-imaging B-star Exoplanet Abundance Study (BEAST), the first survey explicitly targeting 85 young B stars (M>2.4 M_sun) to look for exoplanets around them. While the survey is still in progress, its provisional results -that I will show here- are already intriguing, challenging everything we used to know about giant planet formation under exotic environments.

Luminous Blue Variables represent a very short stage in the life of some massive stars, characterized by significant variability, dense and steady winds, and occasional mass eruptions that rip off the outer stellar layers. By virtue of these processes, LBVs are often surrounded by large and heterogeneous circumstellar structures, like the remarkable Homunculus Nebula around Eta Car, that contain the evolutionary footprint of the parent star. Therefore, these nebulae have been comprehensively studied at optical, infrared and radio wavelengths, resulting in a very accurate portrait of their dust and ionized gas content. However, a crucial piece of the puzzle is missing: a possible molecular counterpart. Such a component was overlooked for decades, but now we know that, under certain conditions, molecules can thrive in the hostile outskirts of LBV stars, despite the hot temperatures and strong UV fields. By investigating this molecular component at (sub)millimeter wavelengths, we can complete the mass-loss record of these challenging sources, learning about the mechanisms behind the eruptions and disclosing their chemical peculiarities. This talk will present the most remarkable findings of a search for molecular gas associated with Galactic LBV stars, focusing on a series of previously undetected warm molecular rings. These structures, displaying unmistakable signs of CNO-processed material, suggest an evolutionary connection that extends beyond the LBV phase. We will discuss the origin of these structures and the role of LBVs as molecular polluters, shedding light on how the most massive stars contributed to the chemical enrichment of the early Universe.

FIRSTv2 (Fibered Imager foR a Single Telescope version 2) is the upgrade of a post-AO spectro-interferometer (FIRST) that enables high contrast imaging and spectroscopy at spatial scales below the diffraction limit of a single telescope. FIRST is currently installed, and routinely used, on the Subaru telescope as a module of the Subaru Extreme AO (SCExAO) platform. It achieves sensitivity and accuracy by a unique combination of sparse aperture masking, spatial filtering by single-mode fibers and cross-dispersion in the visible (600-900nm). The ongoing upgrade aims at using a photonic chip beam combiner, allowing the measurement of the complex visibility for every baseline independently. Using the integrated optics technology will increase the stability and sensitivity, and thus improve the dynamic range. Integrated optics chips working in the visible wavelength range are challenging (in terms of throughput and polarization). Several photonic chips are under characterization in our laboratory and we have installed a first prototype chip in the FIRSTv2 instrument at the Subaru Telescope. I will thus report on the on-sky results obtained with this kind of device, for the first time in the visible. This is the first step towards the full upgrade of FIRSTv2, that will ultimately provide unique capabilities to detect and characterize close companions such as exoplanets, by combining high angular resolution and spectral resolution in the visible.

A fundamental question in astrophysics is how stars get their mass. We know that low-mass stars form from the collapse of self-gravitating prestellar-cores. Since this collapse, young stellar objects (YSOs) acquire mass through the magnetospheric accretion process for up to 10Myr. According to this scenario, the material falls from the envelope through the circumstellar disk onto the central forming-star, following the magnetic field lines. Thanks to new facilities, it has been possible to observe spectroscopically the inner part of the circumstellar disks in the nerby star forming clouds. Therefore, accurate estimates of the mass accretion rate (Macc) and stellar parameters in different stages (early, i.e. ClassI, and more evolved, i.e. Classical T-Tauri stars) of the star formation process have been provided for single stars and binaries. However, if we integrate Macc provided from the observations for the estimated timescales of YSOs, we found smaller masses than we measure. This means that the majority of the mass is set during the first stage of the highly embedded protostellar phase (Class0), where planets start to form, or the accretion process proceeds in a non-steady framework. While we still know much less on accretion on Class0, the nonsteady accretion is proven by the eruptive YSOs, as FUors and EXors, which experience extremely strong bursts on short and long timescales. I will review recent results about accretion, focusing on open questions on early stages, as how the forming-star mass is related to the disk and envelope mass, and the relation between models and observations. 

Previous experiments have shown that in N2-dominated atmospheres lightning can lead to the formation of nitrate (NO3-) and nitrite (NO2-), which could not only have facilitated the origin of life but also sustained the earliest ecosystems. This hypothesis has been difficult to test with the available rock record because geochemical fingerprints of this fixed nitrogen source have not been developed. We present new results from spark discharge experiments in varying atmospheric compositions corresponding to different points of time in Earth’s evolution. We find substantial amounts of nitrate are produced in an N2/CO2 atmosphere. Furthermore, we investigate the effect of lightning on the isotopic composition of the resulting nitrogen oxides in solution. Our fixed nitrogen is depleted in heavy 15N in comparison to atmospheric N2, in line with rock samples older than 3.2 billion years. For the first time we can assess to what degree lightning chemistry may have influenced the origin and early evolution of life. However, the spark in our experiment is much smaller and cooler than lightning channels in Earth’s atmosphere. To extrapolate our experimental results to full-scale planetary atmospheres we complement them with a complex kinetic chemistry network which we use to simulate the atmospheric chemistry of exoplanets and Earth. We simulate the temperature decay both in a hot lightning channel and a cool spark channel, predicting the production rates of nitrogen oxides and other molecules. This allows us to extend our experiments to real lightning conditions and develop observable tracers for lightning chemistry in exoplanetary atmospheres.

Compact star formation appears to be generally common in dusty star-forming galaxies. However, it remains to be understood how systematic compactness is and its role in the framework set by the scaling relations in galaxy evolution. GOODS-ALMA is a 1.1mm galaxy survey over a continuous area of 72 arcmin2 at a homogeneous sensitivity with two array configurations aimed at understanding these questions. In this new version 2.0 we present a new low-resolution dataset and its combination with the previous high-resolution dataset. The latest results reveal that dust continuum emission at 1.1mm prevails, and sizes as extended as typical star-forming stellar disks are rare. A population of galaxies with modest star formation rates, but which exhibit extremely compact star formation with starburstlike depletion timescales unveils. Compact star formation appears as a physical driver of depletion timescales, gas fractions, and dust temperatures. The new findings suggest that the star formation rate is sustained in very massive SFGs, even when their gas fractions are low and they are presumably on the way to quiescence. Gas and star formation compression seems to be a mechanism that allows to hold their star formation rate. 

The observational study of the interplay between galaxy angular momentum and structure in the cosmic web is challenging due to the weakness of the signal. We study the alignments of galaxy spin axes with respect to cosmic web filaments as a function of different properties for galaxies and for their bulge and disk components. We exploit the SAMI Galaxy Survey to identify 3D spin axes from spatially-resolved kinematics and to decompose galaxies into their kinematic bulge and disk components. We use the GAMA spectroscopic survey to reconstruct the surrounding cosmic filaments. We find a strong correlation between the galaxy spin-filament alignment and the mass of the bulge: galaxies with lower bulge masses tend to have their spins parallel to the closest filament, while high-bulge mass galaxies show a perpendicular orientation. This observed link between the flip in the spinfilament alignment and the growth of the bulge can be explained by mergers. Bulges tend to have perpendicular alignments, indicating mergers as their main formation channel; in contrast, pseudo-bulges tend to have a parallel alignment, consistent with secular accretion. Disks show different alignments according to their kinematic features and bulge mass, suggesting varying formation pathways. We conclude that bulge mass is the primary parameter tracing the processes that cause the galaxy spin-filament alignment to flip from parallel to perpendicular.

The extended, fragile, collisional atomic hydrogen (HI) gas discs in galaxies are excellent diagnostic tracers of gravitational and hydrodynamic processes in the cosmic environment they are residing in and also reservoirs for star formation. Within a galaxy cluster, both gravitational perturbations (tidal interactions, harassment, etc.) and hydrodynamic processes (thermal evaporation, ram pressure stripping (RPS), etc.) are at play. However, it is not clear yet which of these processes dominate the transformation of galaxies from star forming and gas rich, to quiescent and gas poor. I am investigating the influences of the global and local cosmic environment on the evolution of galaxies, both from the HI morphologies of galaxies in different locations of cluster substructures and the multiwavelength case studies of the striking galaxies. From the new MeerKAT telescope observations of A2626 volume, I am studying the spatially resolved morphologies of the 219 HI detected galaxies, covering a range of cosmic environments. By identifying the cluster substructures and characterising their environments, I investigate the relative importance and effects of the various physical mechanisms that are responsible for reshaping galaxies. In addition, I am also studying the detailed cases of HI gas stripping in the “jellyfish galaxies”, the extreme examples of RPS with in-situ star formation in the tails. I have analysed the multi-phase (neutral, molecular, ionised gas) ISM of jellyfish galaxies JW100 and JO204 from multi-wavelength MeerKAT or JVLA, MUSE and ALMA observations. I will talk about how HI observations contribute to understanding the multiphase gas stripping in these jellyfish galaxies.

The first epoch of galaxy formation is governed by the infall of neutral, pristine gas. These neutral atomic hydrogen (HI) gas reservoirs will subsequently cool and condense into molecular clouds and initiate star-formation. The HI gas content is therefore a key ingredient in the overall process of galaxy evolution. In the local Universe the hyperfine HI 21-cm transition has been used as the main tracer of this neutral atomic gas, but due to the weakness of the line this approach is only feasible at moderate lookback distances for individual galaxies, even with next generation radio observatories. In this talk I will present a new approach to infer the HI gas mass of high-redshift galaxies, based on an empirical measurement of the [CII]-to-HI conversion factor using gamma-ray bursts. These bright cosmic beacons are used to illuminate the column density ratio of HI and [CII], which provides a scaling between the HI mass and [CII] luminosity per unit column in the line of sight. I will demonstrate how this conversion factor can be applied to recent galaxy samples surveying [CII] out to the edge of the epoch of reionization, at z~6. The HI gas mass is found to exceed the stellar mass at redshifts greater than z~1, and to increase as a function of redshift. Similarly, the fraction of HI to the total baryonic mass of these galaxies is observed to increases from around 25% at z=0 to about 60% at z~6. Further, I will show how the association of [CII] with HI also naturally explains the observed, more extended [CII] emission maps of high-redshift galaxies. I will also demonstrate how this technique makes it possible to infer the cosmic HI gas mass density in galaxies from z~6 to the present, based on estimates of the [CII] luminosity density. These results show the baryonic matter of starforming galaxies in the early Universe is dominated by neutral atomic gas, a vital component to take into account when determining the gas available to initiate and maintain star formation.  

High-redshift quasars can shed light on the co-evolution of central supermassive black holes and their host galaxies in the very early universe. Observational constraints on radio jet and interstellar medium feedback processes are still very limited at redshifts z>2. We investigate the radio-loud quasar P352-15 near the end of Reionization at redshift z~6. This quasar is the most powerful radio emitter with direct evidence of a kpc-scale radio jet (~1.6 kpc) at these high redshifts. I will present the results on the spectral energy distribution of this quasar at millimeter (far-infrared in the rest-frame) and radio observations. The millimeter continuum emission for radio-quiet quasars at these redshifts has usually been interpreted as cold dust and is modeled as a modified black body. However, the analysis on this radio-loud quasar shows that it is not possible to model the millimeter measurements as cold dust alone. I will present evidence of the strong radio synchrotron emission in this source affecting the dust-dominated continuum emission in the millimeter, and implying a break in the synchrotron spectrum. I will further portray the big picture in a dedicated study for the first time on measuring different jet lifetimes based on rest-UV/Optical and radio observations of this quasar. Thus, constraining the black hole - host galaxy formation and jet ejection mechanisms of a quasar in the first Gyr of the universe. 

The usual choice of adopting simple power-law scaling relations to link the total mass of members with their luminosity is one of the possible inherent systematics within strong lensing (SL) models of galaxy clusters, and therefore on the derived cluster masses. I will present how we use the Fundamental Plane (FP) relation to obtain more accurate and complex relations between the observables describing cluster members, and to completely fix their mass from their observed magnitudes and effective radii. Using new information on their structural parameters (from HST imaging) and kinematics (from MUSE data), we build the FP for the early-type galaxies of the cluster Abell S1063. We take advantage of the calibrated FP to develop an improved SL model of the total mass of the cluster core. The new method allows for a reduction of the uncertainty on the value of the core radius of the main DM halo. We also find a different relation between the mass and the velocity dispersion of members, which shows a significant scatter. Thanks to a new estimate of the stellar mass of cluster members from HST data, we measure the two-dimensional, cumulative mass profiles out to a radius of 350 kpc, for all baryonic and dark matter components of the cluster. Finally, I will present a comparison between the physical properties of sub-halo in our model and those predicted by high-resolution hydrodynamical simulations. We find good agreement in terms of stellar mass fraction, and some discrepancies in terms of sub-halo compactness.

The polarization model for one of the future generation telescope, the Thirty Meter Telescope (TMT) will be presented. The polarization ray tracing model gives the complete Mueller matrices of all the mirrors of the telescope. The instrumental polarization and crosstalk are found to be varying significantly with the field of view of the telescope, zenith angle, and the position of the instrument ports due to the inclined tertiary mirror of the telescope. We also propose a design to mitigate the effect of polarization arising from the Nasmyth mirror by using an inclined mirror kept orthogonal to it. The polarization aberrations arising due to the non-normal incidences and coating has been calculated to ascertain its effect on the point spread function of the telescope. The effects of the segments and coating non-uniformities have been studied. These analysis will be useful for the design of the future polarimetric instruments for TMT.

The galaxy luminosity function (GLF) is a basic descriptor of the galaxy population and its evolution though the history of the Universe. I will present a new experimental design using clustering-based redshift inference to measure the evolving galaxy luminosity function. The idea is to exploit the fact that galaxies are not uniformly distributed through space; instead are strongly clustered and it is therefore possible to infer the statistical distribution of distances. We derive the GLF using data from the Galaxy And Mass Assembly (GAMA) survey and the Kilo-Degree Survey (KiDS) to the limits of the GAMA-KiDS photometric catalogue: m_r ~ 23; more than a decade in luminosity beyond the limits of the GAMA spectroscopic redshift sample. We find that the GLF has a relatively constant power-law slope α ≈ −1.2 for M_r < −13, and then appears to steepen sharply. This upturn appears to be where Globular Clusters (GCs) take over to dominate the source counts as a function of luminosity. Thus we have mapped the GLF across the full range of the z~0 field galaxy population from the most luminous galaxies down to the GC scale.

During merging, the tidal forces of a giant galaxy can strip away the contents of a smaller one leaving behind the nuclear star cluster to orbit in the halo of the giant galaxy as a stripped galaxy nuclei. These stripped nuclei hide among the most luminous globular clusters (GCs) in the halo of galaxies and can be challenging to distinguish. The collection of massive GCs and stripped galaxy nuclei are often called ultra-compact dwarf galaxies (UCDs). An exciting confirmation of this theory is the detection of overmassive black holes in the centers of some UCDs, which also lead to elevated dynamical mass-to-light ratios compared with regular massive GCs. Here I present new high-resolution spectroscopic observations of 321 luminous GC idates in Centaurus A. Centaurus A is the closest giant elliptical and may have undergone a significant merger event, thus providing a unique comparison framework for substructures with the Local Group, such as stripped galaxy nuclei. This work represents the most complete catalog of dynamical mass measurements of luminous GCs in Centaurus A. Our results show a bi-modality in the dynamical mass-to-light ratio distribution, with a population of "normal" GCs and a second population with elevated mass-to-light ratios. This bi-modal distribution deviates significantly from the GC distribution in the Local Group. I will also show that massive central black holes of 10% of the luminous GC virial mass can explain the observed elevated mass-to-light ratios, suggesting that some of these luminous GCs in Centaurus A are stripped galaxy nuclei. 

The successful Kepler and TESS missions have discovered thousands of exoplanets and let the community focus on the characterisation of these bodies. One area of research utilises ultra-high-precision photometric and spectroscopic follow-up observations in order to accurately constrain the bulk densities of terrestrial exoplanets. Combining these observables with Bayesian internal structure modelling that uses geological equations of state, we can start to learn about the compositions of planets around main-sequence stars for the first time. Importantly, by studying multi-planet systems we can conduct comparative planetology that can reveal important aspects that challenge our knowledge of planet formation and evolution via the contrastment of the observational and modelling results of a planet against its neighbours. In this talk, I will present observational studies characterising multi-planet systems initially discovered with TESS and followed-up with the CHEOPS satellite and ground-based instruments, such as ESPRESSO. Additionally, I will discuss our Bayesian internal structure and atmospheric escape modelling, and present the results of utilising such models on several key, multi-planet systems observed with CHEOPS that are expected to become cornerstones of exoplanet characterisation due to the questions they raise about planet formation, the system multiplicity, or the amenability to atmospheric observations. Important knowledge about these systems was uncovered via a combination of precise observations using a new generation of instruments and cutting-edge planetary internal structure modelling. Therefore, utilising these resources we are at the beginning of a new era in characterising terrestrial bodies outside of our Solar System that will be strengthened with JWST

According to the core accretion theory, rocky planets form by growing the initial micronsized dust in protoplanetary discs up to the size of a planet. When the grains reach the size of 1 cm, however, the growth process faces a critical stage: the interaction with the disc gaseous component causes the cm-sized grains to drift rapidly towards the central star, becoming unavailable to form planets. Streaming instability (SI) is often invoked as a potential solution, as it promotes rapid dust overdensity formation. In my study, I simulated the action of SI through 2D local simulations, and computed the mm emission of resulting dusty clumps. Although the small size of the resulting dust clumps makes them inaccessible by direct observations (and thus we cannot directly compare the computed emission to the data), it is possible to define observable quantities, from which we can infer the presence of such substructures. By focusing on two observables – the optically thick fraction ff (in ALMA band 6) and the spectral index alpha (in bands 3-7) – I compared the distribution of simulations in the ff-alpha plane before/after the action of streaming instability to recent multiwavelength data in the Lupus star forming region, finding that the action of SI drives the simulations towards the area of the plane occupied by the data. This study therefore suggests that clump formation via SI is consistent with recent observations, confirming that it can be considered a good idate to solve the radial drift barrier to planetesimal formation. 

The mass loss rates of red supergiants (RSGs) govern their evolution towards supernova (SN) and dictate the appearance of the resulting explosion. Particularly important in how stars appear in the run-up to core-collapse, and in how the explosion will appear, is the amount of mass lost through stellar winds in the RSG phase that immediately precedes SN. Specifically, there have been many recent claims in the literature that stars with masses >17Msun must experience an extended period of enhanced mass-loss before SN in which the envelope is entirely lost. To study how mass‐loss rates change with evolution, we focus on measuring the mass‐loss rates of RSGs in a sample of clusters in the local Universe. The results indicate that there is little justification for substantially increasing the mass loss rates during the RSG phase. In fact, I have shown that for the more massive RSG the massloss rates used in evolutionary simulations must be *decreased* by up to a factor of 20. Implementing this new mass-loss rate equation into stellar models shows stars < 30Msun cannot have their envelopes stripped through quiescent winds prior to core-collapse. I will also discuss the potential for extreme mass-loss rate phases that have been proposed to take place over a short amount of time, but with the potential to peel away many Solar masses of material. Ultimately, I will discuss prospects for the single star evolutionary pathway for the formation of Type Ibc SNe. 

For decades, astronomers have been investigating the connection between supermassive black holes (SMBH) and their host galaxies. I will talk about my work based on the largest-yet sample of galaxies with dynamically measured central SMBH masses, which adds another step to this study. We measured the host galaxy properties using state-of-the-art two-dimensional isophotal modeling and the multi-component photometric-decomposition, incorporating the kinematic evidence for the presence of stellar disks. These decompositions allowed us to accurately estimate the galactic spheroid properties and reliably identify the galaxy morphologies. We investigated the BH mass scaling relations for various sub-morphological classes of galaxies, i.e., galaxies with and without a disk, early-type versus late-type galaxies, barred versus non-barred galaxies, and Sersic (gas-abundant accretion/wet merger) versus core-Sersic (depletedcore, dry merger) galaxies. Consequently, we have discovered significantly modified correlations of BH mass with galaxy properties, e.g., the spheroid stellar mass, total galaxy stellar mass, central stellar velocity dispersion, bulge central light concentration, bulge size, and the bulge projected and internal stellar. The final scaling relations are dependent on galaxy morphology, fundamentally linked with galaxy formation and evolutionary paths. These relations provide consistent predictions for the very recent directly measured BHs. The morphological dependence of BH scaling relations poses ramifications for the virial factor and offers tests for simulations and theories for BH-galaxy co-evolution. These relations provide an easier way to estimate BH merger time scales, morphology-aware BH mass function, and improved characteristic strain model for the ground- and space-based detection of long-wavelength gravitational waves generated by merging SMBHs.  

Cold gas is the fuel for star formation and mapping the evolution of the cosmic molecular gas content is therefore key to our understanding of the build-up of galaxies over cosmic time. The advent of large millimeter interferometers now makes it possible to map the cold gas content of the universe in unprecedented detail. In this talk, I will present the latest results from the ALMA Spectroscopic Survey of the Hubble Ultra Deep Field (ASPECS), an ALMA large program that performed the largest three dimensional spectral-scan survey for cold gas and dust through cosmic time. I will discuss the resulting physical properties and conditions inside the cold interstellar medium of star-forming galaxies at cosmic noon, and the implications of ASPECS for the cosmic molecular gas density and the baryon cycle. I will close by discussing key steps we are working on to further refine our knowledge of cold gas in distant galaxies.

ALMA observations have somewhat surprisingly revealed the presence of large amounts of dust in the first generations of galaxies in the Universe. Unfortunately, their dust temperature Td remains difficult to determine due to the limited available FIR continuum data at redshift z>5. This introduces large uncertainties in several properties of high-z galaxies, namely their dust masses, infrared luminosities, and obscured fraction of Star Formation Rates (SFR). We have developed a new analytical method to constrain Td using a single continuum data point at 158 microns by combining it with the overlying CII emission. With our method, one can analyse uniquely the large number of [CII] and continuum detections at high-z provided by recent ALMA Large Programs such as REBELS and ALPINE. REBELS sources analysis allows us to extend for the first time the previously reported Tdredshift relation into the Epoch of Reionization (EoR). We find that Td increases with redshift, but more mildly than previous suggestions based on stacked SEDs fitting at z<4. We produce a new physical model that explains the increasing Td(z) trend with the decrease of gas depletion time, tdep=Mg/SFR, induced by the higher cosmological accretion rates at early times. The model also accounts for the observed Td scatter at a fixed redshift. A dust temperature increase at high-z has testable and potentially relevant implications: (a) it alleviates the problem of the uncomfortably large dust masses deduced from observations of some EoR galaxies, (b) it results in a larger obscured fraction of the SFR.