Is it clear to you, what we indirectly witness when gazing at some recent observations of protoplanetary disks (PPDs)? How do they fit into our theoretical comprehension of planet formation? And what can the oldest known solids tell us about the history of our own Solar System? Well, the last decades of hunting for exoplanets definitely revealed one thing: planet formation is a quite natural consequence of the formation of most stars. Detecting planets or protoplanetary cores in the early stage of their formation can give us immensely valuable information and constraints, both about the planetary product and about its environment. Here at ESO, I will talk about how embedded planetary cores interact with their surrounding PPD. I will give examples of how these effects can lead to observable signatures for ALMA, and how these signatures can in return be interpreted to deliver important information about the environment of planet formation and the planet's motion therein. Besides investigating the direct "live" observation of distant PPDs, I will show that we can also extract some crucial knowledge about the history of our own Solar System by inspecting pristine leftovers of the oldest known solids under the microscope.

Galaxies in compact groups live in an environment where galaxy interactions play an important role, similar to the situation in the early universe. The atomic hydrogen is extremely affected by this environment, whereas the molecular gas is relatively normal in most galaxies.

However, the  properties of the molecular gas are drastically different if one selects those galaxies , based on their mid-infrared colours from the Spitzer and WISE satellites, that are  in transitioning phase from active to quiescent. These so-called “canyon”  or "infrared transition zone" galaxies have a considerably lower molecular-to-stellar mass and star formation efficiency than actively star-forming galaxies in compact groups.

This shows the transition from active to quiescent is driven both by a loss of molecular gas and the fact that the remaining gas has lost its capacity to form stars efficiently.

High-resolution observations with NOEMA and CARMA of a few objects confirm the perturbed nature of the of the molecular gas.

A likely reason for this result is that collisions of the ISM are taking place in the “canyon” galaxies that produce shock and inject turbulent energy into the ISM.  These processes have been observed in several individual objects, as e.g. in the intergalactic medium of the compact group Stephan’s Quintet or in the collisional bridge of the Taffy galaxies. 

Understanding and characterizing the distribution and properties of stars in the Galactic stellar disk and its structure is of fundamental importance to study the evolutionary history of our Galaxy. In this talk, I will discuss the vertical stellar disk structure of MW-like galaxies using the large data provided by the IllustrisTNG50 simulation, the highest-resolution run of the IllustrisTNG suite of cosmological-magnetohydrodynamical simulations. I will present the demographics of TNG50 MW-analogs sample, focusing on the disk flaring: how and by how much the vertical disk scale height increases at larger galactocentric distances. The unique set of a hundred of MW-like galaxies provided by TNG50, allows us to investigate how unique and special our Galaxy is: are the known observational features in place in all TNG50 MW-analogs? How often the disk flaring occurs in our MW-like sample? Across all MW-mass disk galaxies, do young and old stellar populations display the same amount of flaring? Moreover, I will discuss whether the degree of flaring depends or correlates with other structural properties, such as disk heights, disk lengths and the gas fraction.

We have used SCUBA-2 and ALMA to detect 75 sources in 100 square arcminutes of the Chandra Deep Field-South, by far the highest density sample of faint 850 micron sources yet obtained.  The observed region matches the deepest portion of the 7 Ms Chandra image, making it possible to probe low-luminosity AGN at very high redshifts.  We find that most of the ALMA sources appear to be consistent with having both their X-ray and submm emission driven by star formation.  Indeed, only 20% of the ALMA sources have intermediate X-ray luminosities (rest-frame 8–28 keV luminosities of 10^42.5-10^44 erg s^-1), and none has a high X-ray luminosity (>10^44 erg s^−1).  Conversely, we find extreme star formation rates (>300 solar masses per year) in some intermediate X-ray luminosity sources, but not in any high X-ray luminosity sources.  I will discuss how our results seem to be consistent with gas clearing from the galaxies.

Accreting supermassive black holes are thought to drive the energy output in the form of radiation and relativistic plasma outflows (jets) seen in Active Galaxies. As such they allow us an excellent opportunity to probe the realm of extreme physics.

Hosting one of the most massive black hole in the local Universe, the nearby radio galaxy M87 has become a prominent target in this regard with recent campaigns enabling to study astrophysical processes such as jet formation or the production of non-thermal radiation in unprecedented detail.

I will highlight recent results on the high-energy diagnostics of M87, ranging from non-thermal magnetospheric processes in the vicinity of its supermassive black hole to the X-ray characteristics of its large-scale jet.

On black hole horizon scales, gap-type particle acceleration, accompanied by curvature and Inverse Compton radiation, could be responsible for the rapidly variable gamma-ray emission seen by current ground-based VHE instruments, introducing a link between gamma-ray production and jet formation. On larger scales, complex X-ray emission features have been emerging which can be used to distinguish physical scenarios for the origin of the extended X-ray emission in the kilo-parsec-scale jets of AGN. 

The study of dark matter captured inside stars has proved to be a viable indirect search strategy complementary to other direct searches. In this context, only a fraction of the rich diversity of physics found in different types of stars has been explored, with most studies mainly focused in the Sun. In this work we looked to the center of the galaxy and studied the imprint of dark matter particles in two completely different types of stars: low mass main-sequence stars and Red Clump (helium burning) stars. We found that the scattering interactions between baryons and dark matter particles within the central region of these stars can result in effects such as the slowdown of the nuclear burning rate or the suppression of core convection, both of which can have an important impact on the evolution and asteroseismology of the star.

Star-forming galaxies are known to follow broad correlations between their star-formation rate, stellar mass and metallicity.  Yet, many questions remain about the physics behind these relations.  In this talk, I will highlight some recent results on star-forming galaxies at low mass and high mass from two deep spectral surveys in the Hubble Ultra Deep Field (HUDF).  At low masses, we have used the MUSE HUDF Survey to measure the slope and intrinsic scatter in the galaxy main sequence down to unprecedented low masses.  We find an increased scatter and shallower slope than predicted on the basis of theoretical models.  At the high mass end, we are using the ALMA Spectroscopic Survey in the HUDF to measure the molecular gas content in galaxies without any preselection.  We detect a variety of galaxies in molecular gas, that lie on, above and even below the galaxy main sequence, and examine the local conditions in their ISM using CO, [CI] and dust continuum.  I will argue that now is a good time to push MUSE and ALMA as key instruments to forward our understanding of the physics behind the galaxy main sequence at high redshift, both at low and high mass.

From a theoretical point-of-view, magnetic fields are crucial to the evolution of planet-forming disks. However, profound observational constraints are pending. Presently, the number of cutting-edge polarization observations presenting inconclusive data increases continuously. In very recent years, polarization at mm-wavelengths, the classical tracer of magnetic fields, emerged as highly ambiguous, and the pressing demand for comprehensive tools to analyze these new observations is growing. I will present an overview on the sources of continuum polarization with focus on the impact of grain alignment, scattering, and grain porosity on the polarization measurement – as well as a potential solution to this dusty ambiguousness, linearly polarized gas emission.

Though computational methods are widely used in many disciplines, those who author these methods have not always received credit for their work. This presentation will cover recent changes in astronomy, and indeed, in many other disciplines, that include new journals, improved software policies for existing journals, community resources, changes to infrastructure, and availability of new workflows that make recognizing the contributions of software authors easier. This talk will include steps code authors can take to increase the probability of having their software cited correctly and steps researchers can take to improve their articles by including citations for the computational methods that enabled their research.

I present ALCOHOLS, a 2.7 square degree survey in the CO(3-2) line covering a substantial area in the Orion giant molecular clouds A and B. The survey was done using the SuperCAM 64-element receiver array at APEX. I I will present first results, including a first analysis of a sample of more than 70 protostellar molecular outflows that have been extracted from the survey data.

Short of sending spacecraft to an asteroid, the highest-resolution way to learn about asteroids is to study them with radar.  Arecibo Observatory in Puerto Rico is home to the world's largest single-dish radio telescope and the most powerful planetary radar system for asteroid studies.  The 305-meter diameter facility dedicates hundreds of hours a year to improving our knowledge of near-Earth asteroids and comets with planetary radar.  Radar observations reveal a wide variety of asteroids shapes, surface features, and sizes, as well as asteroid moons.  Important not only for robotic solar system exploration of asteroids, radar-derived asteroid shape models help us plan for potential asteroid hazard mitigation and future human exploration of asteroids.  I will show recent results from the Arecibo planetary radar system and discuss the upcoming asteroid sample return mission OSIRIS-REx that launched in September 2016 to return pieces of a 4.6-Gyr old asteroid to Earth.

Gap-opening planets can generate dust-trapping vortices that may be responsible for some recently-discovered crescent-shaped dust asymmetries in transition discs. Although this model can explain some of these features well, most previous numerical studies of vortices have neglected the time it takes to grow a planet to Jupiter-size, a process that may last more than 1000 orbits. In our work, we incorporate more realistic planet formation timescales into two-fluid (gas and dust) hydrodynamical simulations, which we use to generate synthetic ALMA images of planet-induced vortices. With longer planet formation timescales, we show that planets trigger shorter-lived vortices with much more elongated shapes, if they even form at all. Although these elongated vortices still trap dust, that dust is no longer trapped at the center of the vortex. Instead, with a flatter pressure bump and disruptions from the planet’s overlapping spiral density waves, the dust instead circulates around the vortex. This motion spreads the dust out over a wider azimuthal extent (> 180 degrees) and carries the peak off-center (often by > 30 degrees with sufficient resolution). We compare our synthetic images to those from recent disk surveys, and identify candidate elongated vortices. Overall, our work demonstrates that observing elongated planet-induced vortices would help constrain the timescales for planet formation.

It is well known that old stellar populations are dominated by evolved short-lived hot stars (Teff  > 10, 000 K). Such stars emit most of the light in the Ultra-Violet (UV) and have similar optical colours over a wide range of temperatures because the optical passbands are far enough down the Rayleigh-Jeans tail of their spectral-energy distributions. They are therefore inconspicuous in optical images of old star clusters in comparison to the large numbers of main-sequence stars and red giants. But, far-ultraviolet (FUV) and near-ultraviolet (NUV) imaging of old stellar populations provide a unique opportunity for the studies of white dwarfs, blue stragglers stars (BSSs), post asymptotic giant branch star and compact binaries etc. Since they are easily discerned in the rarefied topography of Far UV/Near UV colour magnitude diagrams. Consequently, a number of space missions including Hubble Space Telescope have imaged a number of globular and a few old open star clusters since they are not only ideal objects but also span a broad range of stellar populations in both age and chemistry, as well as a variety of environments.

In light of the above, a key science project on this topic has been identified by the ASTROSAT, India’s first multi-wavelength (X-ray to optical) space-born astronomy mission launched successfully on 28 September 2015.  Life time of the mission is 5 years. Five scientific payloads are mounted on the ASTROSAT. One of them is UV Imaging Telescope (UVIT).  It has spatial resolution of ~1.2 arc-sec, large field of view (~ 28 arc-min diameter) and also has number of filters in both FUV and NUV regions.  UVIT observations, therefore, provide very useful observations for extracting the properties of UV bright stellar populations in a star cluster. A few results published recently will be highlighted in this talk along with future Indian Space mission in UV as well as encouraging capabilities of recently installed Indo-Belgian 3.6 meter optical telescope located in central Himalayan region of India.

The cosmic baryon cycle is key to our understanding of galaxy formation and evolution. Open questions are: How do baryons cycle into and out of galaxies? What physical processes drive the dramatic change in the cosmic star formation rate history? What galaxies harbor half of the star formation activity in the universe enshrouded in dust? I show how we transform ALMA into a survey telescope acquiring more than 2000h of observing time. I present measurements of the molecular gas across cosmic time offering new clues on the evolution of the star formation rate history. Furthermore, I highlight new results from our search for the dusty star-forming galaxies.

Supernovae (SNe) and Long-duration Gamma-ray Bursts (GRBs) are exploding stars and constitute the most powerful explosions in the universe. Since they are visible over large cosmological distances, release elements heavier than Helium, and leave behind extreme remnants such as black holes, they are fascinating objects, as well as crucial tools for many areas of astrophysics, including cosmology. However, for many years the fundamental question of which stellar systems give rise to which kinds of explosions has remained outstanding, for both Type Ia SNe used for cosmology as well as for Superluminous SNe and long-duration GRBs that must originate from special kinds of massive stars. I will discuss the exciting recent progress that we have made on this question in key areas by publishing and thoroughly analyzing the largest data sets in the world at the time. I will conclude with an outlook on how the most promising venues of research - using the existing and upcoming innovative large time-domain surveys such as ZTF and LSST - will shed new light on the diverse deaths of stars.

I will present results from a catalog of ~1.8 million Omega Cen member stars derived from DECam photometry covering a field of view of ~5x5 degrees  across the cluster and HST data for the innermost regions. The unprecedented accuracy of DECam photometry, the depth and field coverage, combined with HST data for the cluster core, allowed me for the first time to derive the global stellar density profile of Omega Cen based on star counts of red-giant and main-sequence stars from 1 to ~140 arcminutes.

The King and Wilson models fail to reproduce the outermost shape of Omega Cen density profile suggesting that the interaction with the Galactic tidal field and the presence of potential escaper (extra-tidal) stars need to be taken into account to explain the observations. The best fit of Omega Cen density profile is found with the SPES models which include potential escaper stars, confirming the presence of a stellar halo around the cluster. 

I will present the results of my master thesis project on quasar feedback and outflows, which have been submitted for publication to MNRAS and announced at https://arxiv.org/abs/1906.00985.

The Active Galactic Nuclei (AGNs) play a major role in the evolution of the galaxies, thanks to their ability to launch powerful outflows. The detection of nuclear X-ray winds, as well as ionised and molecular galactic outflows provide direct evidence of the so called feedback processes in action, whose physics is nevertheless poorly understood. 

I have studied a local AGN hosting a powerful nuclear X-ray wind, using ALMA observations in order to trace, at galactic scales, the molecular ISM kinematics. I found the signature of a possible molecular outflow with v~200 km/s that is potentially able to suppress the star-formation activity. By comparing the energetics of this putative outflow with that of the nuclear wind, I tested the blast-wave AGN feedback scenario favouring a momentum-driven outflow over an energy-driven model. 

I will introduce the scientific background, present the data analysis and discuss the possible interpretations of the results and their implications.

Any viable cosmological model in which galaxies interact predicts the existence of primordial and tidal dwarf galaxies (TDGs). In particular, in the standard model of cosmology (LCDM), according to the dual dwarf galaxy theorem, there must exist both primordial dark matter-dominated and dark matter-free TDGs with different radii. I use the hydrodynamical cosmological Illustris-1 simulation to identify tidal dwarf galaxy candidates and study their present-day physical properties. In particular, I will discuss the positions of galaxies in the radius-mass plane depending on their nonbaryonic content and compare it with observational data. I will explain the implications of the dual dwarf theorem for a LCDM cosmology. Finally, I will discuss the occurrence of NGC 1052-DF2-type objects.

Stellar feedback triggers galactic outflows and is a crucial component in simulations of galaxy formation. Galactic outflows contribute to the continuous interaction between galaxies and their surrounding medium, and allow for the interplay between stars and the different phases of the interstellar medium (ISM).

I investigate the impact of galactic outflow modelling on the formation and evolution of a disc galaxy, by performing a suite of cosmological simulations with initial conditions of a Milky Way-sized halo. In this talk, I will show how sensitive the general properties of the simulated galaxy are to the way in which stellar feedback triggered outflows are implemented, comparing results obtained by adopting different galactic outflow models. I will discuss the key requirements that a feedback model must have to be successful in producing a disc-dominated galaxy and the crucial importance of galactic outflows in reproducing observational features of present-day disc galaxies.

Also, I will show how the inclusion of AGN feedback impacts on the evolution of galaxies and on their properties, and I will discuss the key interplay between AGN and stellar feedback across cosmic time in cosmological simulations. I will focus on how feedback energy from the central BH couples to the different phases of the ISM, how the joint AGN and stellar feedback guarantees the large-scale cosmological accretion of gas on to the forming galaxy, controls the BH growth, triggers galactic outflows, and determines the BH-galaxy co-evolution. 

I will discuss the connection between chemical evolution and gas dynamics, to interpret observations of metal abundance in the ISM and circumgalactic medium. I will also present results that show the impact of the AGN feedback on the metal content of ISM and stars in galaxies, comparing predictions from my simulations with observations. 

Understanding the processes of gas flows in and out of galaxies is crucial in galaxy evolution studies. Yet, observations of the faint and diffuse Circum-Galactic Medium (CGM), where these processes take place, remain challenging.

The most efficient approach to detect this faint and diffuse gas is in absorption towards bright background quasars. However, to investigate the CGM we need to also identify the galaxy counterpart and connect it to the absorption feature.

In this context we characterised counterparts to Damped Lyman-alpha Absorbers (DLAs) at z~1 using HST broad-band images. We measured their stellar masses and find them to be generally less massive than the average galaxy population. We also discovered their complex morphology and environments, challenging the interpretation of CGM studies in absorption.

Beyond absorption, prospects to map the CGM in emission will offer new information on its extent and clumpiness. To optimise observing strategies of the CGM in emission, we have made predictions from dedicated cosmological zoom-in RAMSES simulations. We post-processed galaxy halos with an emission model to create mock integral field observations. Using the instrument model, our results indicate that ELT/HARMONI will enter a regime of low surface brightness typical of the CGM which is not attainable with current facilities.

Powerful quasars can be seen out to large distances. As they reside in massive dark matter haloes, they provide a useful tracer of large-scale structure. Stacking far-infrared and sub-millimeter maps on the locations of quasars has proved a useful tool in studying quasars and their environments. We stack Herschel-SPIRE images at 250, 350, and 500 μm at the location of 11,235 quasars in 10 redshift bins spanning 0.5 ≤ z ≤ 3.5. The unresolved dust emission of the quasar and its host galaxy dominate on instrumental beam scales, while extended emission is spatially resolved on physical scales of order a megaparsec. This emission is due to dusty star-forming galaxies (DSFGs) clustered around the dark matter haloes hosting quasars. We measure radial surface brightness profiles of the stacked images to compute the angular correlation function of DSFGs correlated with quasars. We then model the profiles to determine large-scale clustering properties of quasars and DSFGs as a function of redshift. We adopt a halo model and parametrize it by the most effective halo mass at hosting star-forming galaxies, finding log(M_eff/M_⊙)=(13.8+/0.1) at z = 2.21-2.32, and, at z = 0.5-0.81, the mass is log(M_eff/M_⊙)=(10.7+/-0.2). Our results indicate a downsizing of dark matter haloes hosting DSFGs between 0.5 ≤ z ≲ 2.9. The derived dark matter halo masses are consistent with other measurements of star-forming and sub-millimeter galaxies. The physical properties of DSFGs inferred from the halo model depend on details of the quasar halo occupation distribution in ways that we explore at z > 2.5, where the quasar HOD parameters are not well constrained.

X-ray binaries, composed of a compact object (neutron star or black hole) orbiting around a companion star, constitute an excellent environment to study accretion phenomena, one of the most promising challenges in modern astrophysics. Outstanding open topics include the interplay between outflows (in the form of collimated winds or relativistic jets) and discs, the accretion-radiation energy balance, the radiative feedback and the relation between relativistic jets and the fundamental properties of the black holes (e.g. spin). Here, we report the analysis of two black hole low mass X-ray binaries, 4U 1630-47 and IGR J17091-3624, using X-ray high-resolution spectra. In the case of 4U 1630-47, we found that the absence of lines in the transitional state cannot be attributed to an evolution of the plasma caused by thermal instabilities. For IGR J17091-3624 we identified a local X-ray absorber during a hard-intermediate accretion state. This is the first detection of a local not-outflowing absorber simultaneously with a compact jet emission.

Pyxel is a novel, end-to-end detection chain simulation framework in Python, designed to host and combine existing and new models, i.e. code simulating instrumental effects such as optical diffraction, charge deposition by cosmic rays, charge diffusion, detector Point Spread Function, readout noise sources, Charge Transfer Inefficiency in CCDs or persistence in CMOS-based imaging detectors.

This simulation framework has been developed in order to alleviate the need for re-developing a new specific simulation tool for every new instrument onboard space mission or ground observatories and instead share and transfer resources and knowledge.

Pyxel is an easy-to-use, flexible and multi-purpose tool to support instrument development during all phases, e.g. to generate synthetic data, support data processing and analysis , estimate performance, understand criticalities, investigate problem areas or trade between different technologies.

It is developed at the European Space Agency in collaboration with the European Southern Observatory, and will be released soon as an open-source software. Our goal is to establish a worldwide collaboration based on Pyxel to share simulation codes and resources, initiate and facilitate the knowledge transfer within the instrumentation community.

With available X-ray surveys getting to extreme deep levels with Chandra (~1e-17erg/s/cm2) and probing harder energies with NuSTAR (8-24keV), one may wonder how JWST or ALMA will contribute to obscured-AGN demography. Although deep spectroscopy will be enabled with spectroscopic instrumentation on board JWST (especially with MIRI) and ALMA, such modes are still regarded as follow-up tools for this purpose. This presentation aims at showing how deep high-spatial resolution NIRCam and MIRI broad-band imaging combined with ALMA can excel in what obscured-AGN demography and host-characterisation is concerned with respect to what is currently achieved by X-ray surveys. I will show one way to pursue a telescope-time-efficient survey aiming at selecting AGN up to redshift 2 (and potentially to redshift 6), and what currently planned JWST GTO and ERS projects lack in that regard. Extra science questions such a JWST-ALMA team-up could address in addition "for free" (e.g., high-redshift source selection) will be briefly highlighted.

Central and satellite galaxies are strictly connected to the global and local properties of their host halo, although in very different ways. While the stellar mass of the central galaxy is tightly correlated with the host halo mass, satellites might go through a complex mix of processes involving the erosion of their hot and cold gas and stellar component.

I will show how these connections can be used to understand the distribution of galaxies in the SFR-stellar mass plane up to z~1.2 using SDSS and COSMOS data. I will show that the Main Sequence of star forming galaxies and its scatter as a function of stellar mass are consistent with a re-scaled version of the local relation and distribution, shifted at higher values of SFR according to (1+z)^3. The relations bends at high stellar masses, where central galaxies of massive halos, as groups and clusters, dominate in number. Low mass satellite  dominate the region of quiescence at very low star formation activity at any redshift. I will argue that the MS bending at the high stellar mass end is due to two processes: i) the formation of a bulge component as a consequence of the increased merger rate in groups and clusters, and ii) the cold gas starvation induced by the hot halo environment, which limits the gas inflow onto the disk. The latter process leads to a systematic decrease of the availability of molecular gas at any stellar mass in groups and clusters with respect to lower mass halos. Similarly, the increase of the MS scatter at high stellar masses is explained by the larger spread of star formation histories of central group and cluster galaxies with respect to lower mass systems.

The distribution of planetary companion masses, as well as the integrated surface density of companions over fixed mass ranges provide a wealth of information concerning planet formation processes as well as the subsequent dynamical evolution of planetary systems.  However, decoding this information requires large samples of host stars of differing mass.  Here we review recent direct imaging results (e.g. Reggiani et al. 2016) combining predictions for planetary mass distributions as well as very low mass brown dwarf binaries suggesting a local minimum in the companion mass ratio distribution.  We also present preliminary results for the on-going SPHERE SHINE imaging survey on the ESO VLT (Vigan et al. in preparation).  Using constraints on the surface density distribution of gas giant planets we can fit results from radial velocity, imaging, and other techniques with a log-normal that peaks between 1-10 AU (e.g. Meyer et al. 2018).  Finally, we discuss the implications of these results (the local minima in the companion mass ratio and the local maxima in derived surface density distribution of gas giant companions) as a function of stellar mass.  We explore whether gas giant planet mass functions could be universal when considered in ratio to the host star mass and highlight areas where further work is needed.

We compare resolved and unresolved observations of the CO and dust continuum emission from star-forming galaxies at z~2. The molecular gas phase of the interstellar medium is a crucial component of star-forming galaxies, hosting, and providing the fuel for, star formation. Constraining the total mass and spatial distribution of molecular gas is therefore critical to understanding the evolutionary state of a galaxy, which can be characterised by how efficiently, and where, star formation is occurring. To determine the total molecular gas mass of high-z galaxies, the community currently relies on two main approaches: measuring either (1) a CO line luminosity, or, (2) dust continuum emission. These molecular gas tracers have been observed for large samples of high-z galaxies with ALMA, and it is assumed that the two lead to equivalent measurements of the molecular gas content. But, recent low-resolution imaging indicates that the CO and dust continuum may trace different galactic regions, with the dust continuum emission being more centrally concentrated. In this talk I will present our comparisons of the CO and dust-derived molecular gas properties of Main Sequence galaxies at z~2 and will discuss the implications for future molecular gas studies with ALMA.

Brown dwarfs (BDs) bridge the mass range between low-mass stars and Jupiter-like planets. BDs are relatively abundant in star forming regions and in the field, but their formation mechanism is still under debate.  Some theoretical descriptions and observational findings support the idea that stars and BDs share a common formation history, but the observational evidence is still not enough to distinguish the competing formation models. The study of the earliest phases of BD formation, the proto-BD phase, when they are still embedded in the parental cloud, and finding BDs formed in isolation with similar properties to low-mass stars would strongly support the star-like scenario as the primary formation mechanism. Our group started more than ten years a project to search and characterize very young proto-BD through a systematic and multi-wavelength exploration in nearby star-forming regions. I will show some of the results of the collaboration that has found a few tens of candidate proto-BDs in Taurus, Barnard 30, and Chamaeleon II, which begin to point out to the formation of BDs as a scaled-down version of low-mass stars.

The halo system of the Milky Way is a precious laboratory because it provides unique elemental abundances and kinematic information on the first objects formed in the Universe and encoded in the ancient stars that populate this complex structure. All this information can be used to tightly constrain models of galaxy formation and evolution. In this talk, I will focus on the age distribution and age gradients in the halo system and I will discuss possible formation scenarios of the Galaxy based on these results.

The study of the inner gaseous disc of YSOs is crucial to understand the physical processes ruling disc evolution and its connection with planet formation. In this talk, I will present our results on the inner disc properties of the CTTS RW AurA. The RW Aur system has captured the attention of astronomers for its dimming events. By using X-SHOOTER spectra obtained when the star was in a bright and in a dim state, we compare the NIR CO emission in order to shed light on this mystery. In general, the NIR CO emission traces a warm (T=2000-5000K) and dense (NCO>1e12cm-2) gas as expected in the innermost region of discs. Both states need a cool (T=2600K) and dense (NCO=7e20cm-2) gas to reproduce the observations, with the emitting region located just inside the dust sublimation radius. By comparing the SED (from ~300 to ~1000 nm) and the CO emission of both states, we find that the dimming can be due to absorption by a layer of large grains with optical depth slowly declining from 2.8 to 1.6. The accretion rate remains constant (Macc~2e-8 Mo/yr) if one assumes that the same layer of dust also occults the accretion line emitting region. This excludes accretion bursts as the main cause of RW AurA brightness variability.

In the course of their accretion phase, massive (proto)stars impact their natal environment in a variety of feedback effects such as thermal heating, MHD-driven protostellar jets and outflows, radiation forces, and photoionization / HII regions. Here, I present our most recent simulation results in terms of the relative strength of the feedback components and the size of the reservoir from which the forming stars gain their masses. For the first time, these simulations include all of the feedback effects mentioned above which allows us to shed light on the physical reason for the upper mass limit of present-day stars. Furthermore, we predict the fragmentation of massive circumstellar accretion disks as a viable road to the formation of spectroscopic massive binaries and the recently observed strong accretion bursts in high-mass star forming regions.

To advertise our latest code development, I will also overview the most recent results obtained in a variety of other astrophysical research fields from the formation of embedded Super-Earth planets’ first atmospheres (Cimerman et al. 2017, MNRAS) to the formation of the progenitors of the first supermassive black holes in the early universe (Hirano et al. 2017, Science).

Outflows of evolved stars drive the chemical evolution of galaxies in the local Universe. Population models dictate that low- to intermediate-mass asymptotic giant branch (AGB) stars dominate this process today, while in the early universe, massive stars and supernovae were likely the main contributors. However, many key issues regarding AGB mass loss remain unresolved. Thanks to Spitzer, a number of Local Group galaxies have been observed in detail, revealing the dust-production rates of all evolved stars, and hence the total dust injection rate for the galaxies. However, measuring the gas mass-loss rates outside our galaxy is prohibitive, making it unlikely that a large sample will be available in the foreseeable future, and systematic studies in the Milky Way remain conspicuously absent. The Nearby Evolved Stars Survey (NESS) aims to fill this gap, by targeting a volume-limited sample of roughly 400 sources within 2 kpc, enabling robust statistical studies of local evolved stars. We will derive the dust and gas return rates in the Solar Neighbourhood, and constrain the physics underlying these processes. I will present a detailed description of the project, including the motivation and strategy, and highlight some of our early results. I will also briefly introduce the tools we are developing that will, along with a catalogue containing all raw and reduced NESS data and a compilation of literature data, be released to the community to aid reproducibility.

The study of dwarf spheroidal galaxies (dSph) is of great importance to understand galaxy evolution at the low-mass end. In the Local Group (LG) the majority of them are found to be satellites of the Milky Way or M31. Although the closest ones have been studied in great detail, it is hard to constrain if their present-day observed properties are mainly caused by internal or environmental mechanisms.

To minimize environmental effects and gain an insight into their intrinsic properties, we are studying two isolated dSph galaxies in the LG, i.e. Cetus and Tucana, located far beyond the virial radius of the Milky Way and M31. These isolated dSphs, are also interesting because they break the morphology-density relation in the LG.

In this talk I will present results from a sizable spectroscopic sample of individual red giant branch stars taken with the VLT/FORS2 instrument in Cetus and Tucana dSphs. The spectra cover the near-IR CaII triplet wavelength region, from which we have obtained line-of-sight velocities and metallicities ([Fe/H]). The wide-area coverage of our data allowed us to obtain information on the large-scale kinematical and chemical properties of the considered galaxies, such as the possible presence of rotation, metallicity gradients, and multiple chemo-kinematic components. Results on the Cetus and Tucana dSphs place more stringent constraints on the formation mechanisms that led to their present-day morphology.

Recent observations which resolved the mid-infrared (MIR) emission of nearby active galactic nuclei (AGN), revealed that their dust emission appears prominently extended in the polar direction, at odds with the expectations from the canonical dusty torus. This polar dust, tentatively associated with dusty winds driven by radiation pressure, is found to have a major contribution to the MIR flux from scales of a few to hundreds of parsecs. When facing a potential change of paradigm, case studies of objects with the best intrinsic resolution are essential. One such source with a clear detection of polar dust is a nearby, well-known AGN in the Circinus galaxy. Motivated by observations across a wide wavelength range and on different spatial scales, we proposed a phenomenological model consisting of a thin dusty disk and a large-scale polar outflow in the form of a hyperboloid shell. With detailed radiative transfer modeling, we demonstrated that such a model is able to explain the peculiar MIR morphology on large scales seen by VLT/VISIR and the interferometric data from VLTI/MIDI which probe the small scales. In contrast, while providing a good fit to the integrated MIR spectrum, the dusty torus model fails to reproduce the spatially resolved interferometric data. Our results call for caution when attributing dust emission of unresolved sources entirely to the torus and warrant further investigation of the MIR emission in the polar regions of AGN. We put forth the disc + wind model of Circinus as a prototype for the dust structure in the polar dust AGN population.

Transit spectroscopy is one of the main techniques for exoplanet atmosphere characterisation. Since a lunar eclipse has a similar geometry as exoplanet transit, it can be used to observe the Earth transiting the Sun. In this talk, I will present three lunar eclipses observations and three topics we learnt from these observations: Earth’s transmission spectrum, Rossiter-McLaughlin effect of the Earth transiting the Sun, stellar line’s center-to-limb variations during lunar eclipse. I will also present how we apply these knowledge to exoplanet atmosphere characterisations, especially the detection of sodium, hydrogen and helium in exoplanet atmospheres.

The assumption of a gas-to-dust mass ratio is a common approach to estimate the basic properties of molecular clouds, from (sub)mm continuum observations of the dust. In the Milky Way a single value is used at all galactocentric radii, independently of the observed metallicity gradients. Both models and extragalactic observations suggest that this quantity increases for decreasing metallicity Z, typical of the outer regions in disks, where fewer heavy elements are available to form dust grains. We investigate the variation of the gas-to-dust ratio as a function of galactocentric radius and metallicity, to allow a more accurate characterisation of the quantity of molecular gas across the galactic disk, as derived from observations of the dust.

Observations of the optically thin C18O (2-1) transition were obtained with the APEX telescope for a sample of 23 bright star-forming regions in the far outer Galaxy (Rgc>14 kpc). From the modelling of this line and of the spectral energy distribution of the selected clumps we compute the gas-to-dust ratio and compare it to that of well-studied sources from the ATLASGAL TOP100 sample in the inner galactic disk. The gas-to-dust ratio is found to increase with galactocentric radius, whereas the dust metallicity decreases, the most common situation also for external late-type galaxies, suggesting that grain growth dominates over destruction. The predicted gas-to-dust ratio is in excellent agreement with the estimates in Magellanic clouds, for the appropriate value of Z.

The discussion on the choice and performance of different gridding functions can be dated back to 1960s by Liz Waldram in Radio Astronomy group at Cavendish. In radio interferometry imaging process, the Fourier transform relation between the visibility data and the sky brightness distribution is usually implemented by Fast Fourier Transform (FFT), where a procedure called ‘gridding’ of convolving visibilities with a chosen gridding function is needed to assign visibility values into uniformly sampled grids. The spheroidal function has been widely used to suppress aliasing effects since early 1980s. We proposed "Least-misfit gridding function" under the criteria of minimising the difference between the DFT and FFT results. It is proved to have a better aliasing suppression performance than the spheroidal function on simulated dataset. It also minimises the DFT and FFT difference, outperforming the spheroidal function at least 10^2 times with the same gridding width and image cropping ratio. The least--misfit gridding function with a support width of 7 and an image cropping rate of 0.5 is recommended to be applied both into gridding and degridding process, so as to achieve the single precision in terms of the image misfit and visibility misfit respectively. Its application on our newly proposed wide-field imaging method can achieve the single and double precision with the gridding width equals to 7 and 14 respectively.