Seminars and Colloquia at ESO Santiago

Planets are known to open deep gaps in protoplanetary discs when their mass exceeds a gap opening mass, M_gap. Here we use one- and two-dimensional simulations to study planet gap opening in discs with angular momentum transport powered by MHD disc winds. We parameterise the efficiency of the MHD disc wind angular momentum transport through a dimensionless parameter α_dw, which is an analogue to the turbulent viscosity α_v. We find that MHD disc winds are much less efficient in counteracting planet tidal torques than turbulence is. For a disc in which α_dw∼α_v, M_gap is determined by the disc viscosity rather than the wind. If turbulence is as weak as α_v～10⁻⁴ then M_gap is a factor of a few to ten smaller than previously derived for discs with α_v≥10⁻³ unless α_dw≫10⁻². We generalise the well-known Crida et al. (2006) gap opening criterion for turbulent discs to evaluateM_gap for any values of α_v and α_dw. We conclude that if MHD disc winds are the main driver of angular momentum transfer, then formation and evolution of planets of mass greater than about one Earth mass is very different from that in the viscous disc models. These effects must be taken into account in future population synthesis models of planet formation.

Superluminous supernovae (SLSNe) is a class of intriguing transient objects, extremely bright with an absolute magnitude of M ∼ −21 and quite rare compared to the typical core-collapse SNe. Their extreme luminosities cannot be explained by conventional power sources, so alternative long-lived central engines such as magnetars or black hole accretion, interactions with dense circumstellar material (CSM), and radioactivity have been proposed. In this presentation, I will discuss the peculiar SLSN SN2020zbf, whose spectroscopic features appear unique even among SLSNe, initially leading to a redshift misclassification until we obtained a higher-quality spectrum through our X-shooter program. I will present an analysis of the photometric and spectroscopic evolution of SN2020zbf, including putting it in the context of other SLSNe, and our ongoing analysis of its unusual spectra.

As we enter the JWST era, and are on the threshold of the ELT era, high spectral resolution observations in the thermal infrared will continue to be important.  They may even become more important.  Even with the sensitivity of JWST, the limited spectral resolution means line profiles will often be unresolved and weak features may be hidden by a strong continuum or nearby features.  To fully understand the objects we study with JWST, our current observations show we will need the information provided by high-resolution spectroscopy.  The ELTs, along with new instrumentation, will be important tools in this process.  Of course, the thermal IR spectroscopists dream is to have a cold, space telescope equipped with a high-resolution spectrograph, and I will end with a discussion of a pathway towards that dream.

The Lyman-alpha forest has been used to distinguish between warm dark
matter (WDM) or cold dark matter. Observationally, the flux power
spectrum of the Lyman-alpha forest exhibits a suppression at small
scales.  The origin of this suppression can be due to long-sought WDM
or to astrophysical bias, related to the unknown reionization history
of the Universe. In this talk we discuss previous works, that explored
the scenario of a hot reionization -- now disfavored by cosmic
microwave background observations -- and left little room for warm
dark matter interpretation. We will then give our result for the
constraints on WDM from the flux power spectrum in a cold reionization
scenario, fully compatible with most recent observations.  We will
discuss possible outlooks for constraining the nature of dark matter,
using high resolution quasar spectra.

The recently commissioned James Webb Space Telescope (JWST) is set to become humanity's sharpest eye to look at the infrared Universe. From being able to detect the faint glow of the first galaxies to being able to characterize the atmospheres of Earth-sized worlds, the observatory's unique capabilities will allow it to perform a wide range of exciting science, that will undoubtedly revolutionize our understanding of the Universe. In this talk, I will introduce the new frontiers JWST will be --- and is already --- exploring in the field of exoplanetary science during its very first year of scientific operations, with a special focus on transiting exoplanets. Through some early results on new dimensions being explored for gas giant exoplanets, as well as first looks at the atmospheres and surfaces of small, rocky exoplanets, I will show how JWST is already dramatically changing our understanding of planetary systems in the cosmos, allowing us to put our own Solar System in this exoplanetary context.

Astronomy is one of the most relevant historical activities in Rapa-Nui through centuries. Since many years, archaeoastronomy researches have been made on the whole island, mainly based on the distribution of the moaï, with the conclusions that they clearly show the solstice and equinox directions. Even if the topology of the island has changed through time (construction of the airport, roads etc.), many alignments remain to lead to the conclusion that they were used to fix the annual calendar, with the new year connected to the rising of the Pleiades (Matariki) young open star cluster. Moreover, many petroglyphs and carved flat stones are witnesses of celestial observations (papa uhi etu'u) such as planet movements, comets, novae, supernovae, eclipses etc.

Interactions between radio galaxies and their large-scale environments are key factors to investigate the feedback processes responsible for triggering and fueling AGN activity. To improve our understanding of such interactions, we carried out a multi-frequency analysis based on the comparison of Chandra and VLT/MUSE observations of radio galaxies in the Third Cambridge Catalog. I will focus on the results on 3CR 196.1, the potential first detection of ionized gas filling an X-ray cavity and a prime example of how radio activity can affect the intracluster medium. Lastly, I will present our preliminary results on the optical-to-X-ray comparison of the rest of the sample, which point to a different origin of the ionized gas surrounding radio galaxies as a function of their ionization status. 

Contemporary cosmology is looking at the Universe as a whole and in the talk the ideas, instruments and technologies that are driving today the search of Dark Matter, Dark Energy, Black Holes and the origin of our Universe is presented. These topical researches at the interface between particle physics, astrophysics and cosmology, are offering new challenges and opportunities to each of these fields in a common endeavour. Thanks to the new technologies, instruments and new probes, as well as the current analysis capability, scientists will hopefully provide soon answers, to cosmological questions related to the early universe, thus unveiling new physics and contributing to a big step forward in our understanding of the early and late Universe, a Universe. Asking ourselves “Does the Universe have a beginning?” “Do physical laws and causality apply to the universe as a whole?” is asking scientific questions with a philosophical meaning. In the past and until the 18th century, there was no dividing line. Scientific disciplines and philosophical considerations were often associated in scientific observations; some representations to explain the advancements in natural sciences as well depicted by astronomers can be seen as pieces of art. It is worth to remember that at CERN and elsewhere the Bell theorem with the locality and causality assumptions and the Bell’s inequalities have been debated not only for their scientific but also for their philosophical implications. With the belief that Science, Philosophy and Art are expressions of a common quest: the necessity we pursue since the dawn of time, to understand the world and the universe we are living in and of which we are an integral part, the talk will terminate with a presentation of art work from Enrico Magnani inspired by the Supernova and Dark Matter.

Understanding how many halos are in our Universe is the most crucial test of our cosmological paradigm. So far this test has been limited to the high mass end of the halo mass function in the galaxy cluster regime. However, massive clusters sample only the 2% of the virialized dark matter halo population. Addressing this fundamental problem would require extending the analysis to the bulk of the halo population, in the galaxy group regime. Nevertheles, at this mass scale, our knowledge of the number density of halos and of their properties is still very poor.

The new X-ray telescope eROSITA, extremely sensitive in the soft X-ray band, is revealing an unprecedented number of X-ray groups in the local Universe. Nevertheless, the observed number density is still much lower than the predicted halo number density. This is due to the highly biases eROSITA All Sky Survey (eRASS) selection function. I use the GAMA optically selected groups in the area of the eROSITA science verification survey to understand how many and which halos eROSITA is able to capture. I will review the similarities and the differences of the properties of the X-ray detected and undetected systems to identify the reasons why, at fixed halo mass, many halos still remain invisible in the X-rays.

At present, detecting new rocky planets within the habitable zone and the radial velocity follow-up of transiting candidates are priority objectives of the exoplanetary field. Both, require a great effort including high-precision instruments and state-of-the-art analysis techniques. Additionally, a proper observing strategy is crucial to ensure the effectiveness of the observations, avoiding unnecessary measurements that waste valuable telescope time. In this talk, I will present the KOBEsim algorithm, a Bayesian-based strategy for the detection of planets in radial velocity surveys. It is developed within the KOBE experiment, aspiring at maximizing the detection of potential habitable exoplanets orbiting K-dwarfs. After gathering the first data, it targets the leader orbital period proposing the best next observing date by means of maximizing the Bayes factor, accelerating the detection or rejection of that period. This new approach has demonstrated to improve the detection efficiency in comparison with a conventional strategy of monotonic cadence, achieving a detection in around 50% fewer observations and time span. KOBEsim has the potential to save expensive telescope time in current and upcoming instruments, and to allow the detection of light planets further away from their host star in reasonable time spans.

In the era of Extremely Large Telescopes, the current generation of 8-10m facilities are likely to remain competitive at ground-UV wavelengths for the foreseeable future. The Cassegrain U-Band Efficient Spectrograph (CUBES) has been designed to provide high-efficiency (> 40%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R >20, 000 (with a lower-resolution, sky-limited mode of R ~7, 000). With the design focusing on maximizing the instrument throughput (ensuring a Signal to Noise Ratio (SNR) ~20 per high-resolution element at 313 nm for U ~18.5 mag objects in 1h of observations), it will offer new possibilities in many fields of astrophysics, providing access to key lines of stellar spectra: a tremendous diversity of iron-peak and heavy elements, lighter elements (in particular Beryllium) and light-element molecules (CO, CN, OH), as well as Balmer lines and the Balmer jump (particularly important for young stellar objects). The UV range is also critical in extragalactic studies: the circumgalactic medium of distant galaxies, the contribution of different types of sources to the cosmic UV background, the measurement of H2 and primordial Deuterium in a regime of relatively transparent intergalactic medium, and follow-up of explosive transients. The CUBES project completed a Phase A conceptual design in June 2021 and has now entered the detailed design and construction phase. PDR will take place at the end of November. First science operations are planned for 202

I will report in this talk my work on the AGB star R Sculptoris recently published in A&A. For the first time, the R Scl environment has been observed simultaneously in the infrared  LM and N-bands, allowing me to provide a clear depiction of the location, the nature and state of matter in the close environment of the AGB carbon star. I will demonstrate on this example the power of combining interferometric and spectroscopic analyses based on VLTI/MATISSE instrument data. To manage this, I developed a Bayesian radial profile reconstruction tool,  that was needed to reveal the place of different compounds. This tool, called RHAPSODY, is very complementary to image reconstruction as it provides a higher dynamic range, leading to the confirmation of features detected in the images. I will comment on the paper results and will present the robustness one can expect from this tool.

The European Extremely Large Telescope (ELT) is a revolutionary scientific facility that will allow the ESO astronomical community to address many of the most pressing unsolved questions about our Universe. The ELT is now under construction and with its 39-metre primary mirror it will be the largest optical/near-IR telescope in the world.
I will present an overview of the ELT Programme, focusing on the latest status of the telescope and its instrumentation, and highlight the key science drivers.

Negative feedback from AGN is invoked as the leading cause of galaxy quenching in almost all modern galaxy evolution models. However, observational evidence for feedback on a galaxy population level is lacking, leading to some claims that it is ineffective. In this talk I will summarise the results of my recent project investigating the predictions of population-level quenching in three of the leading cosmological hydrodynamic simulations (EAGLE, IllustrisTNG and SIMBA). By performing similar tests to observational studies, we discover that the simulations do not predict clear evidence for AGN feedback on a population level, despite implementing strong and effective feedback models. This shows that we cannot use a lack of evidence from observations of galaxy populations as proof against AGN feedback. I will also discuss how we can make progress in uncovering the effect of AGN on galaxy evolution, from both an observational and simulation perspective. 

The highly praised ESA Gaia satellite mission has already provided the astronomic community with high quality astrometric, photometric and other data or almost 2 billion stars, and will continue to do so over the next years. As time goes by, the precision of the astrometry increases, with the number of measurements and the time-span during which these are obtained. Thus the correction of systematic effects in the data, such as aberration need to be handled to a point, where the conventional means do not suffice anymore.To accomplish this, a programme was conceived, to track the satellite with highly precise (20 mas) groundbased astrometry to deliver the required data for the optimisation of Gaia's accuracy, called Ground Based Optical Tracking (GBOT). This programme has faced many challenges and uncertainties, as well as set backs, but finally GBOT has come to the point, where its data are being included in the processing of the Gaia astrometry, since 2020. During this presentation, M. Altmann give an overview of the history of GBOT, and the steps taken to ensure final success, after many years of challenges. He will also report on a project searching for asteroids on the existing GBOT data, which has lead to observations of about 50,000 objects, of which about 20,000 were previously unknown. S. Bouquillon will decribe in detail the methods used and tools/codes developed in this frame work to reach the GBOT astrometric requirements. 

In this talk, I present my PhD thesis which studied the observed properties of two "extreme" types of dwarf galaxies in nearby galaxy clusters and further investigated their formation mechanism. After a general introduction to dwarf galaxies, I present my research on "ultra-compact dwarf galaxies (UCDs)", the most compact galaxies observed. The majority of bright UCDs originated from the dense environments in the center of galaxy clusters as the remnant nuclei of stripped dwarf galaxies. To study other possible origins of UCDs, I performed a search for UCDs in the low-density regions of the Fornax galaxy cluster and found evidence for UCD formation outside galaxy clusters, possibly by pre-processing in galaxy groups in the outskirts of the cluster. Furthermore, I present my research on "ultra-diffuse galaxies (UDGs)", the most diffuse galaxies observed. The dark matter content and formation of UDGs have been intensely debated in the past years. In particular, the dark matter content of some UDGs was suggested to be very high, a claim that was supported by the extensive number of GCs around these galaxies which appeared to be inconsistent with expectations from cosmological simulations. By studying GCs of a sample of UDGs in the Coma galaxy cluster, I showed that the previous claims about the GC number and therefore, the dark matter mass of these galaxies are not valid. I further examined the GC of these UDGs and found that their GC number and GC distribution pose challenges for several of the currently favoured UDG formation models. Looking forward, I briefly present the applications of Euclid and LSST for studying these extreme dwarf galaxies within the Local Universe.

Transiting exoplanets provide opportunities for us to observe their atmospheres and to analyse them using spectroscopy. As the characterisation of exoplanet atmospheres relies on the detection of spectrally resolved features, analysis can be improved with high signal-to-noise ratios (SNR) that are possible to obtain with modern spectrographs like CRIRES+ on VLT in Paranal, Chile. However, obtaining high SNR through adjusting exposure times comes with a trade-off. While a higher cadence minimises the spectral feature smearing that arises due to the continuously changing radial velocity of the planet, a lower cadence collects more photons with reduced overheads and readout noise, enhancing the signal-to- noise ratio (SNR) of each observation. As such, there is a need to establish what the optimal compromise is between the SNR and time resolution for a given target. In this talk, a new method will be presented that will aid observational astronomers in establishing the optimal parameters for observing transiting exoplanets with spectroscopic instruments such as CRIRES+ using simulated spectra, cross-correlation, and other statistical methods. This will be particularly relevant for planning ground-based observational studies to characterise atmospheres for objects around cooler stars with more complex stellar spectra.

 Detailed chemical studies of Solar-type stars have long been routine in stellar astrophysics, making possible studies in Galactic chemodynamics and exoplanet demographics. However, a similar understanding of the chemistry of M and late-K dwarfs—the most common stars in the Galaxy and most likely to host planets—has been greatly hampered by the complex molecular chemistry of their cool atmospheres. Here we present a new implementation of the Cannon, a data-driven model widely used in stellar astrophysics, developed for low–medium resolution optical (400–700nm) cool dwarf spectra. Our novel four parameter implementation in $T_{\rm eff}$, $\log g$, [Fe/H], and [Ti/H] models both label uncertainties and missing labels, and is trained on 121 cool dwarf benchmarks—21 of which have literature elemental abundances measured from a warmer binary companion. Under leave-one-out cross-validation, we recover $T_{\rm eff}$, [Fe/H], and [Ti/H] with precisions of 2\%, $\pm0.12\,$dex, and $\pm0.09\,$dex respectively, a precision which allows insight into the giant planet–[Fe/H] correlation for our sample of 65 TESS candidate planet hosts. Our work highlights the importance of precisely known benchmark systems; the promise of data-driven models for chemical analysis of the rich, but challenging to model, optical spectra of cool stars; and the utility of both in studying exoplanet demographics in the era of TESS and Gaia.

Asymptotic Giant Branch (AGB) stars are a major source of molecular enrichment of the interstellar medium and the chemical evolution of galaxies. It is critical to understand the mechanisms responsible, which is possible by studying the gas and dust around these stars. HCN is one of the most abundant molecules found in the atmospheres of carbon-rich AGB stars. The molecule has been detected in various rotational transitions, including the ground and excited vibrational states. These lines arise from the circumstellar envelopes (CSEs) of carbon stars, which help in understanding the physical conditions in the region. The innermost, hotter regions can be probed by vibrationally excited HCN lines that have high upper energy levels of >1000 K . So far, only a handful of carbon stars, most notable the archetypical IRC+10216, have been extensively studied in these tracers.

This motivated us to observe various rotational HCN transitions from within a number of vibrational states towards 16 carbon-rich AGB stars using the Atacama Pathfinder EXperiment (APEX) submillimeter telescope. In this talk, I will show how we use these vibrationally excited lines to understand the excitation conditions present in the envelopes of the sample of AGB stars and discuss the discovery of new HCN masers towards these sources.

On 26 September 2022, the NASA DART probe successfully impacted the Dimorphos asteroid, the smallest component of the binary asteroid system Didymos. The aim of the mission is to measure the effect of the impact on the orbit of Dimorphos, to test the efficiency of the kinetic impactor technique for planetary defence. Since limited in-situ observations were available at and after impact, ground and space-based observations are critical for the success of the mission, but also provide valuable data for the study of asteroid. The asteroids were observed before and after impact with all 4 UTs of the VLT, using the FORS2, VISIR, X-Shooter, and MUSE instruments. This talk will give an overview of the very high quality data obtained at Paranal and how they will allow us to push our understanding of what asteroids are made of.

Active Galactic Nuclei (AGN) are accreting supermassive black holes (BH) at the centre of galaxies, and their most impressive features in optical spectra is the broad-line emission. The intensity of these features depends on the luminosity of the AGN system and also the amount of neutral hydrogen obscuration. This leads to the understanding that the gas emitting broad-lines must be powered by radiation, and localised such that orientation relative to the line-of-sight changes the observed spectrum. This region of gas is known as the Broad Line Region (BLR). Within a 1-10 year timescale, it is not possible for an AGN to pivot along the line of sight, nor is it possible for the luminosity to vary enough for the BLR to stop emitting broad-lines. Of course, such impossibility is observed in the extreme variability objects, Changing-Look AGN. Our work focuses on finding these object using optical data from SkyMapper, and we have successfully found 29, increasing the total to ~100. To achieve a complete Changing-Look sample within currently available data by utilising this method, we construct a complete AGN catalogue from 6dFGS by classifying all of the AGN sources within the database. Finally, I will also talk about my detour ESO project, PKS2004-447.

Supernova remnants (SNRs) drive large-scale shocks that locally enhance the density of the surrounding material but also inject vast amounts of energy and momentum that largely perturb and disperse the Interstellar Medium (ISM). The interplay between these two effects is considered paramount in regulating the star formation efficiency in galaxies. However, how SNRs affect the physical conditions of the ISM is not well constrained from an observational point of view. In this talk, I will present our work aimed to address this question. I will show our study of the large scale shock triggered by the SNR W44 on the molecular cloud G034. I will show how the shock, probed by Silicon Monoxide (SiO) and observed with ALMA, enhances the density of the processed gas to values compatible with those required for massive star formation and has helped to shape the cloud. I will also present our exploratory large single-dish observing program SHREC, aimed to observe the molecular shock tracer SiO(2-1) toward a sample of 30 SNRs known to be interacting with molecular clouds. I will introduce the aim and technical aspects of SHREC and present the first results obtained toward the SNRs IC443.  IC443 is a well known SNR, expanding into and interacting with a nearby toroidal molecular cloud.  Toward the major site of interaction, known as clump G, we estimate the mass of the shocked gas to be 100 Msun. The shock driven by IC443 into this material enhances its density by a factor >10, to value consistent with those required to ignite star formation. Finally, we estimate that between 35-50% of the momentum injected by IC443 is transferred to the nearby molecular material. Our work therefore indicates that the molecular ISM is an important carrier of the SNR momentum and that the SNR-molecular cloud interaction play a crucial role in the regulating star formation in galaxies.

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 observations of a number of high-mass star-forming regions using their jets through NIR spectro-imaging. We observe the molecular hydrogen (H2) jets in the K-band (1.9-2.5µm) as well as the atomic component as revealed by [FeII] at 1.644µm and Brackett gamma at 2.16µm. We compare the geometry of the NIR outflows with the radio regime.

In this presentation, I will introduce two projects that I am working on related to the connections between galaxy mergers and SMBHs. In the first project, motivated by testing the hypothesis that mergers build up the BH-host mass relation., we look for physically-associated dual quasars with separation < 4" in Subaru HSC/SSP footprint. Our published work has reported 6 such systems. Dual quasars are a special phase in the lifetime of a galaxy-galaxy merger when both of the SMBHs are activated. Spectroscopic observations of these systems will allow us to estimate the BH masses of both galaxies using the viral method. And the stellar mass of host galaxies can be measured with SED fitting using HSC photometry and 2D decomposition methods. Therefore, we are able to compare the BH-host scaling relation in mergers with those in single galaxies in the local universe (Kormendy & Ho 2013). We find that mergers typically bring such systems above the local relation, thus, making the BHs over massive. We also found our observational results are inconsistent with Horizon-AGN simulation. 

Mid infrared interferometry gives us the opportunity to study in detail
the dusty structures at the center of Active Galactic Nuclei. MATISSE,
at the VLTI, is a second generation spectro-interferometer that can
combine the light of four telescopes at a time, making possible to use
image reconstruction methods to recover the morphology of the dusty
clouds close to the super massive black hole. Thanks to its high spatial
resolution comparable to the highest resolution ALMA observations, and
its broad spectral coverage we can also learn about the mineralogical
composition and the physical properties of the dust. In this talk I will
tell you about our recent results on the prototypical Seyfert II NGC
1068.  We obtain a map of temperatures and optical depths of the dust
that unveil  an optically thick ring obscuring the central engine at
parsec scales and a less optically thick disk extending to at least 10
pc. We find that the cold obscuring dust is mainly formed by amorphous
olivines and carbon grains. We further combine MATISSE observations and
radio VLBA and ALMA observations to define the position of the black
hole. We conclude that the dusty structures that we see play the role of
the ‘historical torus’, yet the extended emission suggests the presence
of dusty winds.

Through observations made with ESO’s Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO), I am conducting a search for the chemical signature of low mass (~ 1Msun) Population III stars in a near-pristine environment. From simulations of stellar evolution, we expect low mass Population III stars to yield low values of the 12C/13C ratio. In this talk, I will present the first bound on the carbon isotope ratio 12C/13C in one of the least polluted reservoirs of gas in the Universe. I find log 12C/13C > 0.37 (95 per cent confidence) for the Damped Lyman-alpha system at z=2.34. We can therefore rule out the strong presence of 13C in this system. However, we cannot empirically rule out enrichment from low mass Population III stars yet. By considering the lifetimes of the enriching stars, I have investigated the timescale on which this DLA has been enriched. The results of this analysis tentatively suggest that the most metal-poor DLAs may have been affected by reionization quenching. I will end by discussing my ongoing programme extending this investigation across a subset of the DLA population. Ultimately, I hope to showcase that the most metal-poor DLAs are rare and exceptionally useful environments to study early chemical enrichment, reionization, and the first stars.

Type II supernovae (SNeII) are the most abundant terminal stellar explosion in the Universe. They are significant contributors to galaxy chemical enrichment, their high explosion energies affect their environments and hence galaxy evolution, while their high luminosities mean that they can be observed out to cosmologically interesting distances and can be used to measure distances and metallicities. Current consensus is that these explosions arise from the death of massive red supergiant stars. However, exactly which progenitor and explosion properties (initial mass, metallicity, pre-explosion mass, explosion energy) map to which observed transient properties (light curve and spectral diversity) remains unknown. Here, I present the Carnegie Supernova Project SNII sample of around 100 events, and  summarise progenitor and explosion constraints provided by hydrodynamical modelling of their light curves and spectral velocities. We find an excess of low-mass (~10Msun) progenitors that is inconsistent with the initial mass distribution expected from a standard initial mass function. In addition, we conclude that the SN explosion energy is the physical parameter that most influences observed SNII properties. Finally, I provide an outlook of SNII astronomy in the coming decade."

Classically the process of low-mass star formation is subdivided into six key stages, where a single core evolves from a cold, dense prestellar core through to a hot core, with outflows and significant gas-phase chemistry and eventually to a planetary system. In reality, each star formation stage can be more complex. A large fraction of stars form in multiple systems, significantly impacting how protostars evolve. Star formation processes can also be episodic, leading to significant changes in the chemical and physical properties of sources. A particular challenge for low-mass star formation studies is to disentangle effects due to evolutionary stage from other physical differences between different protostellar systems. 

Planet formation seems to be ubiquitous around young stellar objects. In this talk I will explore the conditions for planet formation across different stellar masses and stellar multiplicity, through the scope of ALMA observations. By visiting some of my recent projects, I will also show how the ALMA data can be studied to recover even the finest brightness details of the disks, always aiming to obtain insight into how their future planetary architectures will look like. More about my work in www.nicolaskurtovic.com

The evolution of massive stars is the basis of several astrophysical investigations, from predicting gravitational-wave event rates to studying star-formation, stellar populations and chemical evolution of the Universe. However, 1D simulations of massive stars, especially those above 40 M☉, are subject to serious uncertainties. I present a comparison between five published sets of stellar models (PARSEC, MIST/MESA, Geneva, BPASS and BoOST/Bonn simulations). I show that there are important differences between the predictions, which can lead to strikingly different results in explaining observations of stellar populations such as gravitational-wave event rates. Related article: https://ui.adsabs.harvard.edu/abs/2022MNRAS.512.5717A/abstract

Debris discs represent the last stages of planet formation and as such are expected to be depleted of primordial gas. None the less, in the last few years the presence of cold gas has been reported in ~20 debris discs from far-infrared to (sub-)mm observations and hot gas has been observed in the optical spectra of debris discs for decades. While the origin of this gas is still uncertain, most pieces of evidence point towards a secondary origin, as a result of collisions and evaporation of small bodies in the disc. In this talk, I will present ALMA observations aimed at the detection of CO gas in a sample of eight debris discs with optical gas detections. We detect CO (12CO and 13CO) gas in HD 36546, the brightest and youngest disc in our sample, and provide upper limits to the presence of gas in the remaining seven discs.

Galactic transients widely known as 'red novae' are thought to be stellar-merger eruptions. These systems go through the common envelope phase just before their outbursts and in one case, V1309 Sco, the common envelope evolution was observed photometrically in real-time. I am going to present and discuss new interferometric observations of the Galactic red nova remnants which shed light on their physical properties before and after the merger. By studying these objects, we have a fighting chance to learn about the complex processes that make binary stars collide. I am going to present what we have learned about the systems where a merger was witnessed, including V838 Mon, V1309 Sco, V4332 Sgr, and CK Vul, and they tell us about the physics of stellar mergers and their products.

Narrow-line Seyfert 1 (NLS1) galaxies are a subclass of active galactic nuclei (AGN) identified more than 30 years ago, but still not entirely understood. These objects are likely characterized by rapidly growing low-mass black holes. Interestingly enough, some of them have been detected in gamma-rays, a sign that they can harbor powerful relativistic jets. In this talk I will show how many of their properties indicate that their true nature is that of early-stage AGN in a recently triggered activity phase, and how they are connected to other classes of kinematically young sources. I will also report on the recent discovery, in a handful of NLS1s, of relativistic jets unexpectedly faint at low radio frequencies and extremely variable at high radio frequency. New observations of these sources are showing an increasingly complicated picture, and I will try to outline the different scenarios we are developing to explain this new, exciting phenomenon. 

Ever since 2005, when I was an NSF REU intern at the University of Rochester working on infrared data from the Spitzer Space Telescope, I have been fascinated by the formation of stars.  Once I started my graduate work at UC Berkeley in the late 2000s, the plot thickened, as suddenly, after I helped install the 1.3mm full-polarization receiver system on the CARMA millimeter-wave interferometer, we could infer magnetic fields in star-forming regions by observing polarization from dust -- I've been a huge fan of magnetic fields ever since. It turns out that the magnetic field is a key ingredient in the star-formation process, from the >10 kpc spatial scales of entire galaxies to the <100 au scales of protoplanetary disks.  In this talk, I'll discuss the highlights of the incredible progress that has taken place in the field of magnetized star formation over the last two decades, and will also discuss paths forward for the next generation of star-formation, polarization, and magnetic-field enthusiasts.

After 17 years in the field, I will be leaving academia to begin work as a Data Scientist at The AES Corporation in Indianapolis, Indiana.  As this will most likely be my final presentation as a professional astronomer, I will reserve the final ~third of the talk for an interactive discussion about my transition into industry.

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. 

The Near-InfraRed Planet Searcher (NIRPS) is a new ultra-stable near-infrared spectrograph that is being installed on ESO 3.6-m Telescope in La Silla, Chile. Aiming to achieve a precision of 1 m/s, NIRPS will operate together with HARPS. NIRPS has been designed to explore the exciting prospects offered by the M dwarfs, focusing on three main science cases: 1) High-precision RV survey of M dwarf aiming at detecting Earth-like planets in the habitable zone; 2) Mass (and density) measurements of planetary candidates orbiting M dwarfs from transit surveys, and 3) Atmospheric characterization of exoplanets via transmission spectroscopy. To achieve its science goals, NIRPS is operating in the Y-, J- and H-bands with continuous coverage from 0.97 to 1.8 μm. NIRPS is part of a new generation of adaptive optics (AO) fiber-fed spectrographs. NIRPS uses a 0.4-arcsecond multi-mode fiber, more than half that required for a seeing-limited instrument, allowing a spectrograph design that is half as big as that of HARPS, while meeting the requirements for high throughput and high spectral resolution. The spectrograph is installed inside a cryostat maintained at an operating temperature of 80 K with a stability of 1 mK and an operating pressure of 1.E-5 mbar. In return for the manpower effort and financial contributions of the consortium to design, build, maintain and operate NIRPS for five years, ESO will grant the consortium a period of Guaranteed Time Observation (GTO) corresponding to 40% of the 3.6-m Telescope time over 5 years, leaving ample time for community-driven science topics. 

Preliminary first light was obtained on May 17th and intensive tests are presently on-going with calibrations lamps as well as with the HELIOS solar telescope to prepare the 1st commissioning which will start in June 7th. I will give an overview of this new instrument, its main science goals and the performances obtained since its installation in Chile.

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.

A substantial fraction of the Universe's star formation is heavily enshrouded by dust, and this basic fact has long been a hindrance to the development of a complete picture of galaxy evolution. Now, thanks to the advent of the Atacama Large Millimeter Array (ALMA), our view of dusty star formation at high-redshift is undergoing a radical transformation. I will present recent ALMA observations of the gas, dust, and dust-unbiased star formation in high-redshift galaxies down to ~kpc and even sub-kpc scales, providing key insight into the morphology, dynamics, and ISM physics in these systems. I will also present new ALMA observations shedding insight into dust-obscured star formation in the epoch of reionization (z>6.5). These observations have important implications for our understanding of the formation of the dustiest galaxies in the universe, which will soon be revealed in unprecedented detail by JWST.

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 Lyman alpha (Lyα) line of Hydrogen is the intrinsically strongest nebular line in a galaxy spectrum and a critical tool for the study of galaxies at high redshift. This UV line is used for a wealth of science including galaxy detection, studying the Epoch of Reionization and tracing the circumgalactic medium around galaxies. But the resonant nature of the line means it undergoes complicated radiative transfer in the neutral Interstellar Medium of galaxies, making the connection between galaxy properties and Lya morphologies line profiles unclear.
On the other hand, Lyman Continuum emission produced by young massive stars in primeval star forming galaxies is thought to be responsible for the reionization of the Universe. To ionize the IGM, LyC radiation must first escape the ISM and neutral gas medium of the galaxy. However, the processes leading to both LyC and Lyα escape in galaxies are still not fully understood, partly due to the scarcity of direct neutral gas observations available.
In this talk, I will present results from 21cm observations of local Lyα and LyC leaking galaxies. These galaxies are analogous to galaxies at high redshift and are thus ideal laboratories for detailed observations of processes that enable Lyα and LyC escape. In particular, I will discuss HI observations of Lyα emitting galaxies, and what the 21cm line teaches us on Lyα escape from galaxies. I will also show MeerKAT observations that enabled the first HI imaging of a confirmed LyC leaking galaxy. These two applications illustrate how the 21cm line can be used in the context of multi-wavelength observations to better understand cosmological processes.

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. 

The atmospheres of sub-Neptunes are expected to exhibit considerable chemical diversity, beyond what is anticipated for gas-giant exoplanets. In my talk, we explore self-consistent atmosphere-interior models of sub-Neptunes to explore this chemical diversity and apply this knowledge to the available atmospheric data of GJ 436b and link it with the corresponding plausible internal structures a presented in Guzmán-Mesa et al 2022.

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.

Dense cores are the places where stars are formed within the supersonic Molecular Clouds. These dense regions (n~10^5 cc) are cold (T~10 K) and display subsonic levels of turbulence (Mach ~ 0.5), and represent the initial conditions for both star and disk formation. However, the influence of the parental core properties on the disk formation process is still not well constrained, and it is, therefore, crucial to study dense cores with interferometers to better understand the dense core and disk connection. 

The classical star formation paradigm involves the evolution of the dense core in isolation and with (relatively) static magnetic fields playing a role in slowing down the dense core collapse. The interplay between magnetic fields, turbulence, and initial rotation is key in controlling the formation and evolution of disks. I will show new results from single-dish and interferometric observations to directly test some of these key items in our understanding of star formation.

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.

Massive stars play a crucial role in the Universe. They shape their surroundings by injecting large amounts of energy and momentum and they produce new, heavy elements that are the building blocks of new stars, planets, and life. They are usually observed in close binaries. Due to the lack of observations covering the earliest stages of their lives, the formation process of massive (binary) stars is poorly understood. I will present observational studies of the outcome of massive star formation. I will show the first spectroscopically confirmed population of massive pre-main sequence stars in the giant HII region M17 where we measured their temperature, luminosity, radius, and projected radial velocity. I will discuss their multiplicity properties and present evidence for the hypothesis that massive stars are formed in binaries with wide orbits that shrink in the first few million years of evolution.

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.

The peak epoch of cosmic star formation also broadly coincides with the peak in the cosmic co-moving molecular gas mass density, at z ~ 2. Even with sensitive interferometers, only strongly lensed galaxies offer the feasibility to efficiently and systematically detect multiple emission lines tracing the full CO ladder and both atomic carbon fine-structure lines for high-z galaxies. In the past few years, our team has delved into the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts (PASSAGES) in order to conduct such systematic studies to better understand the most active star-forming galaxies in the early Universe. In this talk I will present the results of a state-of-the-art approach to model -- simultaneously -- both the detected emission lines and the dust SED. Using the largest assembly of ~200 CO/[CI] lines for any uniformly selected high-z sample, we have explicitly derived the infamous alpha conversion factors without assuming any excitation corrections or typically applied values. I will discuss the implications based on such spatially unresolved measurements, including a detailed perspective on the often-used dust continuum approach to deriving the molecular gas masses. I will also briefly present our current understanding of the [CI] line excitation conditions in the context of these detailed radiative transfer models.

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.

History seems to repeat itself in the domain of extragalactic dust-obscured star-formation studies. The first mapping observations in the nineties revealed a population of galaxies with unsustainably-violent bursts of star-formation, only seen through the dust-obscured emission coming from the birth-clouds of stars. Now that our observations peer further into the high-redshift Universe, we find that even for the youngest observed galaxies (z ~ 8 and beyond), dust-obscured star-formation is far from negligible. Starting from a sample of bright submm selected galaxies from Herschel surveys, I will detail the ongoing progress in exploring the unique star-forming environments, both on the scales of resolved individual observations to the formation of the largest structures in the Universe (i.e., protoclusters). Then, I will expand on our current understanding of high-z star formation through direct ISM tracers, focusing on ongoing and future observations with ALMA that will complement the imminent JWST. 

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.

The making of new stars takes place inside molecular clouds, where dust obscuration limits the use of the classic techniques of optical astronomy.   The study of stellar formation became feasible only when radio and infrared astronomies developed in the second half of the past century. In the 1950s, a new class of bright optical nebula was discovered: the Herbig-Haro (HH) objects. Mysteriously, these nebulae kept on shining without an embedded star to provide the energy.  The presently accepted solution to the enigma is that the HH objects are regions shock-excited by jets from remote, embedded young stellar objects. The first observational results in the study of the formation of new stars revealed outflowing motions, in contrast to the expected infalling motions needed for a star to grow in mass from some sort of initial seed.  After decades of research we now count with a paradigm that explains this and other paradoxes. Stars do form from the contraction of fragments of the molecular clouds and the process involves simultaneous outflow (traced by the jets) and infall (traced by the protoplanetary disks) motions. We are getting close to a deep understanding of our origins through the study of stellar and planetary formation in space.

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.

Recent observing campaigns have revealed a great diversity in exoplanetary systems whose origin is yet to be understood. How and when planets form, and how they evolve and interact with their birth environment, the protoplanetary disks, are major open questions. Protoplanetary disks evolve and dissipate rapidly while planets are forming, implying a direct feedback between the processes of planet formation and disk evolution. These mechanisms leave clear imprints on the disk structure that can be directly observed. 

In the past few years, high-resolution observations of protoplanetary disks obtained in the infrared scattered light and in the millimeter regime have led to exquisite images and shown that small scale structures are ubiquitous in protoplanetary disks, and could result from the dynamical interaction with embedded planets. I will present recent observational results on protoplanetary disks, that allow to probe the disk structure and the dynamics of solids, and in particular, in the so far unique system that hosts two directly imaged protoplanets, PDS70.

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.  

Classical Cepheids - famous for their period-luminosity relation (PLR) - are the most extensively used distance indicators, and a crucial rung in the cosmic distance ladder, which enables to determine the Hubble constant. Majority of classical Cepheids are binary stars, yet the contribution of companions' light has been long assumed negligible and lacked thorough, quantitative evaluation. With more and more detailed theoretical models, that incorporate the effect of metallicity, overshooting, rotation, etc. on Cepheid luminosities on one hand, and more and more precise ground- and space-based observations of Cepheid brightnesses on the other, this assumption can no longer hold. I present an extensive collection of synthetic populations of binary Cepheids for the Milky Way and the Magellanic Clouds, which serves as a tool to quantify the contribution of companions' light to the total brightness of the systems. This light excess shifts the zero point of the PLR, which now can be recognised as a systematic error associated with the PLR, and, by extension, with the Hubble constant. 

Luminous high-redshift (z~6) quasars provide a window to study the most massive and fastest-growing black holes in the young (< 1 Gyr) universe. The elemental abundances in the broad-line regions (BLRs) of these quasars trace chemical evolution in the nuclear regions (< 1 pc) of massive galaxies and provide clues on the early co-evolution of supermassive black holes and their host galaxies. Using 16 high SNR and high-resolution spectra of high-redshift quasars from the ESO-VLT X-shooter Large Program XQR-30 supplemented by 9 additional Gemini-N/GNIRS spectra, we measure the flux ratios of rest-frame UV broad emission-lines, and compare them against photoionization models to derive metallicities in quasar BLRs. Our measurements are consistent with predictions based on emissions from gas clouds that are several times super-solar in metallicity. We also explore correlations based on quasar properties and show how emissions from quasar outflows affect the measured line ratios. Our results suggest rapid chemical enrichment in the cores of massive galaxies in early cosmic time.

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 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 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 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. 

Weak gravitational lensing - small distortions of photon paths due to the large-scale structure of the Universe - is an emerging cosmological probe, in particular thanks to the so-called "cosmic shear". I will present some of the results of today's main cosmic shear surveys, with a focus on the ESO Kilo-Degree Survey (KiDS) in which I take part. I will also discuss some other weak lensing studies with KiDS, including smaller-scale investigations of galaxies and their dark matter haloes, and briefly present my contributions to KiDS galaxy selection and redshift estimation for such analyses. Using KiDS as an example, I will describe some challenges that weak lensing surveys are facing. Finally I will mention two next-generation cosmic shear surveys currently planned: Euclid and LSST.

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.  

The physical and chemical conditions in the earliest stages of formation of Solar-system analogues are fundamental in unveiling the chemical composition of protostars and its impact on planet formation. Simple molecules and more complex organic and prebiotic species are found in the ice and gas as they are being transferred from the molecular clouds into the planet-forming disks and planetary cores and atmospheres. Therefore, to understand how life originates around Solar-like stars, it is essential to trace the chemical evolution during the first few hundred thousand years of star and planet formation.

I will present recent work in which we use a suite of Atacama Large Millimeter/submillimeter Array (ALMA) datasets in Band 6 (1 mm), Band 5 (1.8 mm) and Band 3 (3 mm) at spatial resolutions 0.5 – 3 arcsec for 16 protostellar sources. This is an effort to pinpoint chemical tracers to the physical components of the young protostellar systems at the Solar System scales (50 au). I will put our results in the context of the recently launched James Webb Space Telescope (JWST). From protostars targeted in our work, 12 will be observed by JWST with MIRI and NIRSpec observations. ALMA provides a kinematic map of components for which JWST will deliver the sub-arcsecond observations in near- and mid-infrared for the first time.

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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. 

Circumstellar discs are essential for high-mass star formation. Also, binarity appears to be an inevitable outcome. Indeed, the vast majority of massive stars are found in binaries (up to 100%). Our understanding of the geometry and physical properties of the innermost regions of discs around massive stars and their associated binarity is sparse due to a lack of observational guidance. In this talk, I will present the first systematic study towards a sample of Massive Young Stellar Objects (MYSOs) as observed with long-baseline near-infrared K-band interferometry on VLTI (GRAVITY, AMBER). Geometrical models are employed to derive the characteristic size of the 2μm continuum and ionised gas emission towards this sample of MYSOs and investigate binarity. MYSOs are placed in a luminosity-size diagram for the first time, and their location is directly compared to their low and intermediate-mass counterparts. In addition, the investigation on the origin of the ionised gas emission (Brgamma) points towards a disc-wind interaction. Finally, I will present the first statistics on young high-mass binarity tracing 2-300 au separations and directly compare them to their pre-main and main sequence equivalents, reporting an increasing fraction with evolution.