Mg II resonance doubles are an excellent tool for the kinematics of cold medium. Furthermore, the line ratio of Mg II lines is suggested as the LyC tracer in the epoch of reionization through JWST. Because of the resonance nature, Mg II lines can experience scattering processes like Lya photons in the cold medium. Scattering allows us to get additional physical properties of the scattering medium. Even though the scattering cross-section of Mg II is slightly larger than that of Lya, Mg II photons are not much optically thick due to the small Mg II fraction ~ log Mg/H ~ -5.5. We develop a 3D Monte-Carlo Mg II - Lya radiative transfer simulation. This presentation shows a surface brightness profile, a spectrum, and an escaping fraction of Mg II compared with those of Lya.

The strongest HI absorbers, the damped Lyman-alpha absorbers (DLAs), in QSO spectra indicate the presence of a gas-rich galaxy close to, or along, the QSO sightline. Identifying the HI-selected galaxies associated with DLAs provides a unique opportunity to connect the properties of high-z galaxies to those of their circumgalactic mediums, as well as to identify and characterize galaxies without a luminosity bias. We have hence been using NOEMA, the JVLA, and ALMA to carry out searches for redshifted CO emission from galaxies associated with DLAs at z>~2.

Combining our results with ALMA studies from the literature, we find that the highest-metallicity DLAs tend to be associated with galaxies with very high molecular gas masses, > 5 x 10^10 solar masses, while the galaxies associated with lower-metallicity DLAs are not detected in their CO emission. We have also used the JVLA to detect, for the first time, CO(1-0) emission from high-z HI-selected galaxies, allowing us to measure the excitation of the mid-J CO rotational levels. We find that all four HI-selected galaxies at z>2 with CO(1-0) studies show high excitation of the mid-J CO rotational levels, with near-thermal excitation found in the two galaxies with CO(1-0) detections. The mid-J excitation in the HI-selected galaxies is consistent with that in main-sequence and sub-mm galaxies at z>2, but significantly higher than that in main-sequence galaxies at z<2. The CO-detected galaxies are faint in our HST NUV images, indicating that they are highly obscured objects.

Astronomy's current model of galaxy evolution is built on a foundation of hierarchical growth, in which small galaxies merge together to form larger ones.  In addition to the simple accrual of mass, this merging process is predicted to fundamentally change the galaxie' properties, such as dramatic morphological transformations, the triggering of bursts of star formation and high rates of accretion onto the central supermassive black hole.  In this talk I will explain the physical processes behind these predictions, and present the observations that we are performing in order to test the theory.  Although many of the predictions are indeed borne out by experiment, there have been some surprising conflicts as well, that demand revisions to our models of how mergers shape galaxy evolution.

The birth of the first stars, black holes and galaxies heralded the end of the cosmic Dark Ages and the beginning of the Cosmic Dawn. The light from these objects heated and ionized almost every atom in existence, culminating in the Epoch of Reionization (EoR): the final major phase change of the Universe. This final frontier of astrophysical cosmology is undergoing a transition from an observationally-starved epoch to a "Big Data" field. This process is set to culminate with upcoming observations of the redshifted 21-cm line: providing a 3D map of the first billion years of our Universe. The patterns in these maps are driven by UV and X-ray radiation from the first galaxies, as well as physical cosmology. I will showcase a Bayesian, data-driven, forward-modeling framework to understanding astrophysics and cosmology from the Cosmic Dawn. I will demonstrate how preliminary 21-cm data from the Hydrogen Epoch of Reionization Array (HERA), when combined with other EoR and galaxy observations, already constrain the heating and ionization history of the Universe. High mass X-ray binaries (HMXBs) are mostly likely responsible for heating the intergalactic medium before the EoR, and current HERA limits imply that the first HMXBs were more luminous than local ones, consistent with theoretical arguments based on binary evolution in low metallicity environments.

Single-lined spectroscopic (SB1) O-type binaries are ideal objects to search for elusive black hole (BH) companions and are indispensable for establishing the natal mass ratio distribution of stars. In this talk, I will present an overview of the binary properties of the massive stellar content of the Tarantula nebula of the Large Magellanic Cloud, focusing on recent work on the SB1 population using the technique of spectral disentangling. I will discuss new results regarding the mass-ratio distribution of massive stars at sub-solar metallicity, and present results for the first dormant black hole ever uncovered outside our Galaxy.

The Standard Model of nature's laws provides no explanation for the fundamental constants, like electromagnetism's strength, alpha. It is therefore up to experiments to test whether fundamental constants are, indeed, constant and universal, or instead vary and depend on other physical parameters. I will describe a new probe of alpha's constancy within our Galaxy, solar twin stars, and show our first results which have an ensemble precision of 12 parts-per-billion. This is already the best astronomical measurement of any fundamental constant so far. The results derive from archival high-resolution optical spectra (HARPS) from the ESO 3.6-m telescope, so there is considerable scope for extending them using larger facilities. Our goal is to map alpha across the Milky Way and, importantly, its widely-varying dark matter density field. This will be a completely new, direct test of physics beyond the Standard Model. I will report our discovery of the most distant solar twins and analogues, up to 4kpc closer to the Galactic Centre, as the first step towards that goal, and outline current and future work.

The origin of high-energy neutrinos is fundamental to our understanding of the Universe. Apart from the technical challenges of operating detectors deep below ice, oceans, and lakes, the phenomenological challenges are even greater. The sources are unknown, unpredictable, and we lack clear signatures. Neutrino astronomy therefore represents the greatest challenge faced by the astronomy and physics communities thus far. Immense effort has been put into identifying galactic and extragalactic sources of TeV-PeV neutrinos but still to no avail. I will discuss recently results and our current efforts in understanding the highest energy particle processes in the Universe.

The cosmic web is a complex network of structures that fills the Universe, composed of galaxy clusters at the nodes, connected among them by filaments and separated by large voids. Filaments are elongated, one-dimensional structures which are much more elusive than clusters due to their lower density. The advent of wide-area, large-scale spectroscopic galaxy surveys has allowed us to start investigating the properties of the filaments (and of the cosmic web in general) and to understand their nature. In particular, how filaments connect to clusters and how these connections impact cluster evolution is a hot topic in astrophysics. The average connectivity (number of connected filaments) of a few observed and simulated cluster samples has been measured and it has been demonstrated that it scales with cluster mass. Filaments connecting to clusters have also been detected in the gas phase, either as bridges of matter connecting pairs of clusters or as the tip of gas structures visible at large radii from the cluster center in X-ray observations. In Malavasi et al. 2020, we applied a cosmic web detection algorithm (DisPerSE) to the Sloan Digital Sky Survey (SDSS) to detect the filaments of the cosmic web from the galaxy distribution. We then looked at the position of the Coma cluster of galaxies and we detected three secure filaments connecting to the cluster. This discovery lead to the developing of a further investigation based on constrained numerical simulations. This kind of simulations allow to reproduce in detail a portion of the nearby Universe, recreating observed clusters including Coma. We are currently performing an analysis of these simulations, aimed at reproducing the observed distribution of the filaments connected to Coma with the aim of studying their evolution throughout cosmic history and determining the impact of matter accretion channeled through these structures on the evolution of the Coma cluster. In this talk I will review the results of Malavasi et al. 2020 and introduce the results we obtained with the study of our constrained numerical simulations.

The Milky Way's centre is the closest galaxy nucleus and our Galaxy's most extreme environment. In spite of occupying less than 1% of the Galactic disc's volume, this region was responsible for up to 10% of the entire Milky Way's star forming activity over the past 100 Myr. Therefore, the Galactic centre is the most active star forming region of the Milky Way when averaged over volume, constituting a perfect laboratory to understand star formation under extreme conditions, similar to those in starburst or high-redshift galaxies. However, there are only two known young clusters at the Galactic centre, that account for <10% of the expected young stellar mass. In this talk I will discuss the challenges hampering the observation of the Galactic centre and will present our results on the Sagittarius B1 region, where we find evidence for the presence of several 105 solar masses of young stars that formed ~10 Myr ago. This is a large step towards a more complete census of young stars and opens the field for a better understanding of star formation at the Galactic centre, such as the fate of young clusters and the possibly different initial mass function in this region.

Many molecules have been observed in protoplanetary disks with ALMA, but each molecule probes a different part of the disk. Understanding the full 2D temperature and density structure in a protoplanetary disk is crucial to understand planet formation. For example, planet formation is expected to be enhanced at the water snowline, the midplane radius where water freezes-out. The water snowline can be traced with HCO+, a molecule that very strongly reacts to the desorption of water. In this talk I'll discuss how HCO+ can be used to find the water snowline. Furthermore, I'll use the rarely observed 13CO J=6-5 transition to measure the temperature in the cavities of transition disks and find out if planets could be carving these deep cavities.

The discovery of the first exo-planet around a sun-like star in 1995 revolutionized Astronomy. In just ~25 years, we went from not knowing if the Solar system is a fluke of Nature to realizing that it is totally normal for stars to have planets. It is now clear that planet formation is a robust process, as planets are found around stars more and less massive than the Sun and as planetary systems have been identified in increasingly complex architectures, including other 8-planet systems or planets around binary stars. Relating this diversity of planetary systems to their formation is now a major research area, attracting worldwide large investments in new facilities and staff. The overall objective of the Nucleus for Planet Formation (NPF, of which I was the director until April) is to obtain a better understanding of the planet formation process that will finally allow us to predict what type of planetary systems form under which conditions. We tackle this goal by combining all three branches of modern astronomy: observational and theoretical astrophysics, as well as the technical development of new astronomical facilities. This approach had not only the goal to bring us closer to answering fundamental scientific questions, but also help to convert Chile from a nearly pure user of the astronomical facilities built in the country to a fully grown up and internationally acknowledged partner in all aspects of modern astronomy. In this talk I will highlight some of the results produced by the members of NPF between the end of 2017 and now.

Star formation in our Galaxy typically occurs in low and intermediate-mass environments counting a few 10^2, 10^3 stars. However, a few more extreme star forming environments exist, where hundreds of thousands to millions of stars form in dense regions, often in single events of star formation. Often called “starburst regions”, they are quite rare in our Galaxy today, with a few examples known, while they are common in galaxies experiencing epochs of intense star formation activity (such as interacting galaxies) and in the early Universe.

With a distance of 3.87 kpc from the Sun, and an estimated initial mass of 52000 solar masses, Westerlund 1 is the closest starburst cluster to the Sun. It offers the unique possibility to study star and planet formation, the early stellar evolution and the physics of compact objects in a starburst environment.

In this talk I will present the EWOCS project (Extended Westerlund One Chandra, and JWST, Survey) which is based on a 1Msec Chandra/ACIS-I Large Project, oncoming JWST observations of Westerlund 1, and other data at high spatial resolution (GEMS/GSAOI, HST, etc..). I will discuss the objectives of the project and present the status of the art of data analysis.

The Antikythera Mechanism is the first computer in human history. Built during the 2nd century BC, it was retrieved in 1901 from an ancient shipwreck and is nowadays partially preserved in 82 petrified and fragile fragments. Its functions and use remained a mystery until recently. With the use of innovative techniques, we now know that it was a mechanical model of the cosmos, an advanced machine that displayed the position of the Sun, the Moon and the five naked-eye planets on the sky. The recently formed solar, lunar and first planetary theories of ancient greek astronomy were converted into elaborate axles and gears that calculated the exact positions of the celestial bodies. To its basic function, many more had been added, such as a lunisolar and an astronomical calendar and the prediction of eclipses, resulting in a highly complex machine, fully covered with dials, pointers and texts. The Antikythera Mechanism is nowadays the unique preserved artefact of the technical sophistication that these models of the cosmos finally reached.

I will describe recent results in our efforts to 'observe' cosmological hydrodynamical simulations, with a particular emphasis on the low-density gas in the Universe, from the circumgalactic medium (CGM) around galaxies to the intergalactic cosmic web. Forward modeling lets us create synthetic observations: to test the simulations, interpret recent data, and guide future observations. In particular, emission from hydrogen and metals in diffuse gaseous components is a powerful probe. Combining the IllustrisTNG simulations with resonant line radiative transfer modeling we study predictions for extended Lyman-alpha and MgII halos around galaxies, and the chance to 'directly image' the cosmic web in emission, with an eye towards observability with instruments such as VLT/MUSE, Keck/KCWI, and HET/VIRUS.
 

Debris disks are young analogs of the Kuiper belt of the Solar System. Km-sized bodies collide with each other, releasing large amount of small dust grains that we can detect in near-IR scattered light observations. In this talk, I will discuss what we can learn from such observations, with a special emphasis on the properties of the small dust particles. I will also discuss some of the possible pitfalls that we need to account for when modeling these observations, namely the vertical scale height of the debris disks.

A semi-empirical model is presented aiming at exploring the incidence of X-ray selected Active Galactic Nuclei (AGN) in massive clusters of galaxies (>3 x 10^{​​​​​​14}​​​​​​ M_{​​​​​​\odot}​​​​​​) to z~1.25 and constraining the role of small scale environment (<1 Mpc) in triggering accretion events onto supermassive black holes. Comparison of the model predictions with observations suggests differential evolution of the X-ray AGN fraction in clusters relative to the field. At low redshift, z~0.2, high density environments appear to suppress X-ray AGN with respect to the field. In contrast, at redshift z~1.25 the fraction of X-ray AGN in massive halos is enhanced relative to the field expectation, particularly in the case of high accretion luminosity events, log(L_X(2-10 keV) (erg/s)) > 44. These findings  point to a strong and redshift-dependent influence of the small-scale environment (<1 Mpc) on the growth of black holes. Our results are discussed in the context of different physical processes occurring in dense environments (e.g. ram-pressure, interactions) that could be responsible for the observed trends of the X-ray AGN fraction with environment.

Feedback from Active Galactic Nuclei (AGN) is a main ingredient of cosmological simulations, as well as the possible driver of the AGN/host-galaxy coevolution. If AGN regulate the star formation (SF) of the host galaxy, they should act on the molecular gas content, that is fuel also for the SF. Nonetheless, results in the literature are controversial: local host galaxies are indistinguishable from non-active ones, while high-z AGN are usually CO depleted, yet typically selected because powerful (log(L[bol])>46) and/or as good candidates for hosting outflows. To fill this observational gap, two surveys of unbiased, high-z, X-ray-selected AGN were conceived to investigate the link between SF and AGN-driven kpc-scale ionized outflows: SUPER (z~2–2.5, logL[bol]~44.2–47.8) and KASHz (z~1–2.5, logL[bol]~43.5–46.3). The SUPER team recently found that significant CO depletion is present only in the most massive host galaxies (log(M[star]/M[sun])>11), demonstrating the importance of using unbiased samples representative of the AGN population at cosmic noon.

I will present a study on the total molecular gas content of KASHz AGN (as traced by ALMA observations of CO in Band 3 and 4), covering a wider redshift and bolometric luminosity range than the SUPER ALMA sample. I will report on how the molecular gas reservoir of KASHz sources relates to the properties of their host galaxy (stellar mass, rate of SF), as retrieved from SED fitting. By means of a control sample of non-active, PHIBBS galaxies, matched in stellar mass, rate of SF and redshift, I will show that CO depletion is not significant in KASHz AGN. I will then compare our results to those of the SUPER survey and discuss the different outcome when we also include literature high-z AGN in the analysis.

In this talk I would like to present the study of the Hydra I cluster, at z∼0.012, which is a target of the VST Early-type galaxy Survey (VEGAS). The observations of the cluster were obtained at the Very Large Survey Telescope (VST), using the Omega-CAM instrument, in the SDSS g- and r-bands.
Deep images allowed to map the galaxy structure out the regions of the stellar halos (down to mu_g~28 mag/arcsec^2), to detect the diffuse intra-cluster light components and the population of low-surface brightness (LSB) galaxies (i.e. dwarfs and ultra-diffuse galaxies).
In particular, we studied  how the LSB galaxies  are distributed in the cluster, in order to map the mass assembly of the Hydra I cluster. We discovered that galaxies are grouped in substructures in different regions of the covered cluster area. The non-uniform spatial distribution of galaxies supports the conclusions of Arnaboldi et al. (2012); Lima-Dias et al. (2021), for which several small galaxies are falling through the cluster core, feeding the cluster mass assembly process.
This study motivated a spectroscopic follow-up with MUSE@VLT, which has been approved a large program in P108. This project will be also presented in my talk.

Astronomy is host to a wide variety of so called inverse problems. That is problems, where we have a fairly good understanding of how the fundamental physical properties of a system give rise to corresponding sets of observables (via e.g. simulations), but where the inverse, i.e. recovering the underlying properties of the system from the observations, is a much more difficult task and often subject to degeneracy. Invertible Neural Networks (INNs) are a deep learning approach that is particularly well suited to solving degenerate inverse problems, as they can predict full posterior distributions for the physical parameters of interest.

In this talk, I will give a short introduction to INNs and how they solve inverse problems, and introduce several applications in astronomy that our group is working on. The latter include among others the recovery of stellar physical parameters from photometric observations with the Hubble Space Telescope and the 3D density reconstruction of dust clouds based on thermal dust emission maps. 

Cosmological simulations represent excellent tools to study the formation and evolution of structures in the Universe.
In recent years, improved numerical methods, increased computing power and a better understanding of physical processes have made it possible to reproduce many astrophysical observables at different scales. In this regard, clusters yield a special position: being the largest gravitationally bound systems in the Universe and having formed at late times, they are expected to still retain traces of the main mechanisms involved in structure formation. I will revise the dynamical properties of the cluster's central regions, specifically of the brightest cluster galaxies (BCGs) and the surrounding diffuse intracluster light, addressing the connection with their host cluster. I will highlight the support that simulations can provide to interpret several aspects and systematics included in observations which cannot be disentangled otherwise, such as the expected contribution of intracluster light in these measurements. At last, I will revise future and ongoing projects.

The Magellanic clouds are a great training ground to understand galaxy interactions and formation within the local group. Many models try to explain their origin and interactions with one another and the Milky Way. Unfortunately, due to significant uncertainties in measurements, many parameters of these models are only loosely constrained. However, these limitations are currently changing. Large scale surveys such as Gaia and VMC enable new methods to study the kinematics of this pair. The proximity of the Large and Small Magellanic Cloud (LMC and SMC) provides a unique opportunity to explore the kinematics of resolved stellar populations within an interacting pair of galaxies with exceptional resolution. Their past interactions created many tidal features, such as the Magellanic Bridge and Stream, distributed across vast regions in the sky and containing several star populations. The kinematics of those individual populations can provide insight into the past of the Clouds.

We developed a new method to distinguish between Magellanic and Milky Way stars based on a machine-learning algorithm combining VMC, Gaia, and the latest StarHorse distance estimates. This approach increases the number of Magellanic sources compared to previous studies. As a result, we can now study the kinematics of stellar populations in more detail. Our results show clear implications for future modelling of the Clouds. Our residual proper motions show a stretching on the northern and north-eastern sides, which could be due to the influence of the Milky Way. While the residuals in the southern region implicate a connection with the impact of SMC at the most recent interaction between the LMC a few hundred million years ago, agreeing with newer model predictions. Our approach also enables a search of Magellanic sources connected to the stellar component of the Magellanic Stream, with location, extents and kinematics that are still less studied than the gaseous component.

It is well known that early-type (elliptical and lenticular) galaxies are more common in denser environments. This morphology-density relation implies environment plays a significant role in the formation of early-type galaxies and the transformation between morphological types. However, the physical processes that lead to the relation are still debated. To address this question we use Convolutional Neural Networks, trained on real galaxies, to perform `visual' classification of galaxies in the EAGLE simulation. I will discuss how modern hydrodynamical simulations can reproduce the galaxy morphology-density relation and offer insights into its origin.

Dust is integral to the physics of galaxy evolution and impact the observed SEDs. I present a framework to investigate dust properties combining physics relevant to dust evolution with hydrodynamic simulations. In this model, dust grains form in stellar ejecta and are processed in the ISM via grain growth, grain-grain collisional processes, and destructive processes. Utilizing large-volume cosmological simulations, I present the scaling relations between dust-to-gas ratio with other galaxy properties, and show the evolution grain size distributions with a focus on Milky-Way mass galaxies. I discuss physical processes driving the evolution of dust properties and their impact on extinction features. Additionally, I show results from isolated galaxy simulations with an explicit ISM and feedback model SMUGGLE, and discuss the cause of different types (e.g. Milky-Way type, or SMC-bar type) of extinction laws.

Constraining the high redshift galaxy ISM properties provide crucial input for models of galaxy formation and evolution, and regarding the feedback processes that regulate galaxy growth. Recent ALMA measurements have revealed bright [O III] 88 micron line emission from galaxies during the Epoch of Reionization at redshifts as large as z ∼ 13. We introduce an analytic model to help interpret these and other upcoming [O III] 88 micron measurements. We cross-check our model by comparing it with detailed CLOUDY calculations, and find that it works to better than 15 per cent accuracy across a broad range of parameter space. Applying our model to existing ALMA data at z ∼ 6–9, we find the [O III] 88 µm line observations leave a degeneracy between the gas density and metallicity in these systems. We derive lower bounds on the gas metallicity and upper bounds on the gas density in the H II regions of these galaxies. These limits vary considerably from galaxy to galaxy, with the tightest bounds indicating Z>=0.5Z_solar and nH <= 50 cm^−3 at 2 − σ confidence. We quantify the prospects for breaking this degeneracy using future ALMA observations of the [O III] 52 µm line. We show that either successful detections of the 52 µm line, or reliable upper limits, will lead to significantly tighter constraints on ISM parameters. The forecasted improvements are as large as ∼ 3 dex in gas density and ∼ 1 dex in metallicity for some regions of parameter space.

Great progress is being made with ground-based millimeter wavelength surveys. We highlight some recent results from the Atacama Cosmology Telescope (ACT), which has been conducting large area surveys (up to half sky) since 2014. Measurements of the Cosmic Microwave Background (CMB) temperature and polarization power spectra provide constraints on the Hubble constant that are consistent with Planck satellite measurements, and evidence for tension between CMB and late-Universe constraints on the Hubble constant (Choi et al. 2020, Aiola et al. 2020). Future ACT results including more data are expected to improve on Hubble constant uncertainties from Planck for the first time. Intriguingly, fitting models of early dark energy (EDE) to Planck data do not find evidence for EDE, while fits to the ACT power spectra provide modest support (~3 sigma) for EDE compared to the Lambda-CDM cosmological model (Hill et al. 2022). The half sky ACT survey is also leading to exciting results related to stellar transients (Naess et al. 2021) and the detection of the largest catalog of Sunyaev-Zeldovich (SZ) galaxy clusters (>4000 optically confirmed) yet. We review these results and briefly describe future prospects with ACT data and the upcoming CCAT-prime and Simons Observatory surveys.

We recently reported the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration (T ~ 270 days), high-magnification microlensing event MOA-11-191/OGLE-11-461, in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of six years, reveals a clear relativistic astrometric deflection of the background star's apparent position. Ground-based photometry is used to derive the parallax, and VLT spectroscopy is used to characterize the source. Combining the photometric, astrometric, and spectroscopic measurements, we obtain a lens mass of 7.1 +/- 1.3 solar mass and a distance of 1.58 +/- 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its BH nature. Our analysis also provides an absolute proper motion for the BH. The proper motion is offset from the mean motion of Galactic-disk stars at similar distances by an amount corresponding to a transverse space velocity of ~45 km/s, suggesting that the BH received a natal "kick'' from its supernova explosion. Our mass measurement is the first ever for an isolated stellar-mass BH using any technique.

The pronounced horizontal metallicity gradient along the Milky Way’s bar suggests that the inner Milky Way has a complex formation history. In this talk, I present mean metallicity, age, and orbital maps of the inner Milky Way built using the orbits of ~30,000 APOGEE Dr16 stars with Gaia kinematics integrated in a state-of-the-art bar-bulge Milky Way potential with a slow pattern speed. These maps reveal that the Galactic bar gradually transitions into a stellar inner ring. This ring is radially thick, vertically thin, and elongated along the bar’s major axis. I will explain how the presence of the inner ring, which is on average solar in metallicity and roughly 6 Gyr in age, explains the steepness of the bar’s horizontal metallicity gradient as well as how we can use the ring to give a rough estimate of the bar’s age.

The baryon cycle is a vital ingredient to galaxy evolution models. It describes how atomic gas in galaxies cools, becomes molecular, forms stars and is exchanged with the environment via outflows. The details of the underlying processes (refuelling, outflows, metal transport, etc.), however, are not well constrained, yet. The key information lies in the circumgalactic medium (CGM), a diffuse, low surface brightness gas phase at the interface between galaxies and the intergalactic medium. The CGM can be efficiently studied from absorption features in unrelated background quasars that act as a cosmic beacon.

We advance this emerging field by studying the baryon cycle within absorption-selected galaxies. We combine observations of the ionised gas and stars (with VLT/MUSE) with those of the molecular gas - the direct fuel for star formation (using ALMA) to study the relation between the absorbing gas and the host galaxy. This combination allows us to study the complete baryon cycle. We discover a more complex structure than a one-to-one correlation between absorber and host from both optical IFU observations and ALMA observations of the molecular gas. We characterise for the first time the molecular gas excitation conditions. With our holistic approach to trace the entire baryon cycle we shed new light on these most important processes shaping galaxy evolution.

Although substantial progress has been made over the last decades on our understanding of star formation it is mostly in terms of formation of individual isolated stars. However, we know that many stars are formed in star clusters or in clustered environments. Here, the proximity of other stars and interactions between them can alter the formation of each star and thus their final properties, for example their mass. Little is known about the formation of particularly massive star clusters and their content. This is due to a combination of limited suitable targets to observe and limited sensitivity and spatial resolution of observations. As a consequence there are limited observational constraints on cluster formation models. However, in recent years suitable candidates of massive star clusters in their formation have been found. I will present our findings for several of those covering an order of magnitude in mass.

I will further discuss the end product of the star formation, the Initial Mass Function (IMF) in massive resolved star clusters. Through deep high spatial resolution imaging we have probed the low-mass content of the clusters. From this we can directly compare the derived IMF with that determined for the field and low-mass clusters. Further, through dynamic mass estimates we can determine if the clusters will remain bound or dissolve and be a component of the future field star population.

The Planetary Nebula Luminosity Function (PNLF) that goes back to the empirical discovery of an invariant bright cut-off, regardless of Hubble type and metallicity of the host galaxy, has been used since 1989 as a distance indicator for galaxies with a distance of up to ~20 Mpc. Based on narrow-band filter photometry in [OIII] 5007, mainly using 4m class telescopes, this distance range has been explored to saturation. We have found, using MUSE datacubes from the ESO Archive, that a new differential filter technique (DELF) is capable of providing [OIII] photometry with unprecedented sensitivity and accuracy, thus expanding the reach of PNLF distances out to > 30 Mpc, with a distance modulus accuracy of 0.04 mag. I will review recent MUSE PNLF work of several groups, present the benefits of the DELF approach, and explain the potential to measure Ho with this new, independent technique.

In Astronomy, interferometry is an observational technique that delivers us the major resolution possible to study physical processes at the smallest spatial scales that we can probe with our instruments. It is used extensively at radio wavelengths and, since more than a decade, it has been converted into an important technique for infrared Astronomy. Nowadays, the new generation of Very Large Telescope Interferomery instruments have allowed us to recover infrared milliarcsecond-resolution images with good quality to perform detailed scientific analysis from them. As part of the Guaranteed Time Observation’s program of GRAVITY, we have used image reconstruction to analyze several Young Stellar Objects with the aim of depicting their complex morphologies. In this talk, I will give a quick overview of the imaging techniques used in infrared interferometry and, I will highlight their usability with on-sky Hergibg YSO observations taken with GRAVITY at the VLTI.

The eROSITA Final Equatorial-Depth Survey (eFEDS) is a 140 square degree area observed during the performance verification phase of eROSITA. It was observed at a similar depth to the expected exposure in the final all-sky survey in equatorial regions. In this area, we detect 542 clusters. We have studied the morphological properties of the eFEDS clusters by modelling how these properties depend on redshift and luminosity. Using a novel technique, we combine 12 morphology estimators in a single measurement that indicate the relaxation state of the detected clusters. We further investigate the underlying cluster populations (with relaxed and unrelaxed morphology) in the eFEDS cluster sample and find that a simple unimodal distribution is always preferred in this sample. Finally, we investigate the redshift evolution of the relaxed cluster fraction and find no evidence for significant redshift evolution. I will present the methods and results of this work, which you can find at arXiv:2106.15086.

Dust is one of the most important components of the ISM in galaxies. It is a key element in determining the physics and chemistry of the ISM, has crucial roles in the star formation process, and shapes the UV-to-IR SED of galaxies across cosmic time. At Cosmic Noon, z~1-3, most of the energy of galaxies with masses >1e9 Msun is radiated at dust-reprocessed IR wavelengths, yet our understanding of the properties of dust in typical galaxies at these redshifts is far from complete. In this talk, I will show the results of our deep targeted ALMA band-6 continuum survey of ~30 galaxies at z=2.1-2.5, tracing the Rayleigh-Jeans tail of the dust emission. We have robust gas metallicity and SFR estimates for the sample from a suit of optical emission lines, including Hb, [OIII]5008, Ha, and [NII]6585, from the MOSFIRE spectrometer on Keck (the MOSDEF survey). Combining the ALMA continuum observations and Keck spectra with the Spitzer 24um and Herschel 100, 160, and 250um photometry, we study, for the first time, the evolution of the IR SED and dust masses with metallicity at z~2, and compare them with those at z~0. Our data indicates an evolution in the shape of the IR SED with metallicity at z~2, as well as an order of magnitude evolution in dust masses at a given metallicity from z~0 to 2.

I will conclude the talk with a JWST/MIRI prospect. As part of the JWST MIRI HUDF Survey (US MIRI GTO program), we plan to observe the mid-IR dust emission of z~1-3 galaxies in all 8 bands of MIRI from 5 to 28um, providing a very low resolution (R~5) mid-IR spectra. These rich observations will provide constraints to better characterize the IR SED of Cosmic Noon galaxies -- in particular, the relative contribution of hot dust continuum emission and aromatic bands in the mid-IR spectra -- for the first time down to the LIRG regime and below at z>1.

I will present the first results on galaxy clusters from the eROSITA early observations and multiwavelength follow-up, with an emphasis on eFEDS, a 140 deg2 proof-of-concept mini-survey conducted during the PV phase. We detected 542 candidate clusters as extended sources in the eFEDS survey, and studied their X-ray properties with eROSITA data. I will overview the eFEDS galaxy cluster catalog, and highlight the scientific results we obtained on the eFEDS clusters. I will also briefly introduce our most recent progress on galaxy clusters in the eROSITA All-Sky Survey.

The relative impact of different quenching mechanisms in galaxies at different cosmic epochs is still unknown. In particular, the relation between these processes and morphological transformation remains with understanding gaps. In this work we study the relation of star formation variations in the past 300 Myrs in galaxies with different morphologies. For a sample with ~14,200 spirals and ~2,500 ellipticals, our main findings are: elliptical galaxies in the green valley have shorter quenching timescales, in accordance with the major merger scenario; massive asymmetric spirals are the main galaxies bursting in the green valley, following the scenario where minor mergers can trigger star formation and disturb their morphology. Lastly, we present a broader scenario for galaxy evolution in the colour-magnitude diagram following our recent findings.

The Hubble Space Telescope archives can hide many unexpected treasures, such as trails of asteroids, showing a characteristic curvature due to the parallax induced by the orbital motion of the spacecraft during the exposures. I present recent results from the www.asteroidhunter.org project, exploring the ESA Hubble Space Telescope archives with citizen science and deep learning for serendipitously observed asteroids and artificial satellites in orbits higher than Hubble's. We find 1700 asteroid trails in the past twenty years of Hubble observations, most of them being faint and yet to be identified. Additionally, we measure, for the first time, the fraction of Hubble images impacted by artificial satellites for different instruments, filters, and as a function of time, showing that satellites can impact not only observations from the ground but also those from low-Earth orbit. Finally, I will argue that a combination of citizen science and artificial intelligence methods is an efficient way of exploring increasingly large datasets by taking full advantage of the intuition of the human brain and the processing power of machine learning, thus enhancing the scientific exploitation of data archives.

The majority of AGN growth is likely to be in heavily obscured phases, but how do these appear? Are they transient phases that are quickly lost, or can we see stable states of complete obscuration? Using the massive dataset of SDSS/BOSS optical spectroscopy along with the all-sky WISE IR survey, I selected quasar-bright galaxies, with AGN-like mid-IR colours, but lacking major optical signatures (principally [O III] emission). These are AGN that may represent an interesting and understudied phase in the obscured growth of AGN. In this talk I will explain the motivation and methodology of this search, and present some details of the Optically Quiescent Quasar population.