The evolution of galaxies is closely connected to the gas environment in which galaxies reside. Traditionally, this tenuous gas that cycles in and out of galaxies has been studied primarily in absorption using quasar spectroscopy. The deployment of large integral field spectrographs at 8 meter telescopes, and in particular MUSE at VLT, is now transforming our view of the interplay between the ambient gas and galaxies by enabling spectroscopy in emission at very low surface brightness. In this talk, I will present highlights from multiple large programmes that are starting to shed light onto the link between gas and galaxies as a function of cosmic time.

Theoretical arguments suggest that the energy released by the black hole at the center of most galaxies may play an important role in shaping the properties of the interstellar medium (so-called AGN feedback). In particular, AGN-driven, galaxy wide massive outflows may not be a rare and peculiar phenomenon, but a fundamental process affecting the bulk of the baryons in the universe. Hundreds of hours of observations from the ground have been used in the last decade to characterize such outflows and their impact on the host galaxies using e.g. NIR IFU on 8-10m telescopes to trace the ionized gas or the molecular phase with ALMA.  

I will report on the first results of a recently completed Large Programme with SINFONI/VLT (SUPER) on a sample of AGN at z~2. SUPER aims to address the following questions: a) demography of AGN driven outflows on a statistical sample of AGN at cosmic noon; b) how the properties (e.g. energetics and geometry) of such outflows are connected with the properties of the central SMBH; c) which is the impact of such outflows on the gas content of the host galaxy.  

I will finally describe further developments in this research area using facilities that will become available in the future (e.g. JWST, ELTs, SKA, Athena).

When, in theoretical physics, we attempt to derive the quantum properties of a black hole, several difficulties are found on our way. In this talk it is shown how these difficulties can be overcome, but not without reformulating some of the laws of nature. This is very important to know, because this way one might uncover new features of the gravitational force when subject to the laws of quantum mechanics.

We claim that the evolution operator for the quantum black hole during short time intervals can be deduced unambiguously from standard quantum field theory in curved space-time, merely by demanding unitarity and completeness for pure quantum states. We explain its Hilbert space and the topologically non-trivial space-time that emerges in our approach. Since there are no run-away solutions, the behaviour at arbitrarily long time scales follows unambiguously. Curiously, string theory does not seem to work flawlessly when details at the Planck scale are addressed.

One of the most exciting opportunities offered by the new VLT beam combiner GRAVITY is to directly resolve the immediate regions around the super-massive black holes (SMBHs) in the center of active galaxies (AGN), i.e. the Broad Line Region (BLR) and the hot dust ("torus") structures. We are exploiting this capability to study the inner workings of AGN in the K-band on unprecedented micro-arcsecond (sub-pc) spatial scales. This has led to the first interferometric detection of a BLR (finding ordered rotation and measuring the black hole mass in the quasar 3C273), as well as to the first 0.2 parsec resolution K-band image of the dust sublimation region in the nucleus of the Seyfert 2 galaxy NGC1068 (finding a ring-like structure which is inconsistent with the expected signatures of a geometrically and optically thick torus). I will summarize these and other recent results , discuss their scientific (and historical) context, and give and outlook how such observations (along with already planned or potential future upgrades of GRAVITY) might contribute to the study of the structures and physical processes around SMBHs or to the study of how SMBHs build up their mass across cosmic time.

The lower edge of the radio window (10-200 MHz) has been scarcely explored due to the complexity of such observations. In this talk I will review the recent progresses in the observation of the metre-wavelength sky, focusing on the last results obtained with the Low Frequency Array (LOFAR). Then, I will summarize the recent scientific outcomes obtained with LOFAR observations. From the search for radio emission from exoplanets, to the AGN life-cycle, to the study of diffuse radio emission in galaxy clusters. I will conclude presenting the first data release of the LOFAR 2m sky survey at 150 MHz and an sneak preview of the upcoming LOFAR LBA Sky Survey at 50 MHz.

The outskirts of clusters make the best, and most efficient locations to observe and trace the mass assembly processes of the Cosmic Web. Residing at the vertices of this Cosmic Web (Bond et al. 1996), galaxy clusters grow by steady accretion of matter from the surroundings, as well as by discrete mergers with nearby groups and clusters. Supported by simulations, this scenario regarding the total mass content and distribution in filaments themselves remains largely untested. Filaments are vital elements of the cosmic census, containing up to half the baryonic mass of the Universe as a ‘warm hot intergalactic medium’ but also the majority of the dark matter.

Recently, some of the most massive and disturbed clusters have been the centre of attention thanks to the Hubble Frontier Fields (HFF) initiative, which constitutes the largest commitment ever of Hubble Space Telescope (HST) time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters. These clusters were chosen for their strong lens properties, and are all highly disturbed objects, showing major and minor merging on-going processes, making them ideal target to trace the Cosmic Web assembly.

While combining strong- and weak-lensing regimes to map the total mass with X-rays observations of the hot gas and spectroscopy of cluster galaxies to look at their direction of motion, we can thus study the dynamical scenarios in place within these massive galaxy clusters, and trace the substructures engaged in these processes. I will present the last results we obtained on the HFF clusters, and discuss the different caveats present on both the observing and simulation sides. I will then present the BUFFALO HST large programme, the ’spatial extension’ of the HFF, that started back in July 2018 and should end in June 2020.

Type Ia supernovae have long been used as probes of the expansion history of the universe. Their standardisable luminosities make them very attractive as distance measures, and they remain indispensable in constraining the properties of dark energy. In this talk, I will give an update from the Dark Energy Survey (DES), including the latest cosmological results using type Ia supernovae to measure the dark energy equation-of-state. I'll also show how large imaging surveys, such as DES, are developing our knowledge of the 'zoo' of cosmic explosions, beyond the classical supernova types. I'll focus on two new classes of explosion: superluminous supernovae, ultra-bright explosions now confirmed out to a redshift of two, and which bring the possibility of measuring distances at higher redshifts than type Ia supernovae; and 'calcium-rich transients', faint-and-fast events that play a critical role in chemical enrichment, and have a surprisingly high intrinsic rate. Finally, I will look forward to what the next decade of LSST and massive spectroscopic follow-up may bring.

The direct detection of gravitational waves from merging black holes by LIGO in 2015 has revitalized the area of gravitational wave astrophysics. The origin of black hole and neutron star mergers is still unclear, however, and various scenarios have been proposed. In this talk, I focus on the evolution of multiple-star systems such as triples, quadruples, and binary systems in galactic nuclei. I discuss the complex interplay between dynamical, stellar, and binary processes in these systems. Finally, I highlight future directions for modeling their long-term evolution, in order to make predictions for future gravitational wave observations.

It is often said that the Milky Way can serve as a 'model organism' to explore and understand the physical mechanism that shape galaxies from random initial fluctuations into the beautiful island universes we see today.

This statement is true, but easily said and much harder to make a reality. Over the last years I have collaborated with a number of students, post-docs and visitors at MPIA combining spectral surveys and now Gaia to turn this Galactic Archeology mantra into astrophysical insights.

In this talk I will synthesize some of this effort, focusing on two aspects of our Galaxy's main component, its disk: what sets the overall radial profile of the disk,  and what sets its vertical structure? The answers to both questions are linked to the question of how much dynamical memory loss our Galaxy has incurred --  its exceptionally quiescent history. I believe we are now considerably closer to understanding why disk galaxies look the way they do.

In recent years, the number of known galaxy clusters at high redshift has grown dramatically thanks in large part to the success of surveys utilizing the Sunyaev Zel'dovich effect. In particular, surveys carried out by the South Pole Telescope have facilitated the discovery of hundreds of new distant clusters, allowing us to trace, for the first time, the evolution of clusters from shortly after their collapse (z~2) to present day (z~0). In this talk, I will highlight recent efforts by our group to understand the observed evolution in the most massive clusters, including: the enrichment history of the intracluster medium, the merging history of clusters, the cooling and formation of cool cores, the growth of central cluster galaxies, and the evolution of the central radio-loud AGN.  In addition, I will attempt summarize the current state of ongoing and planned SPT surveys, and the synergies with current and future observatories including eRosita and Athena.

The Milky Way halo consists of old and metal-poor stars amidst bound substructures such as globular clusters and satellite dwarf galaxies. A comparison of stellar abundance ratios and kinematics between typical halo stars and these bound substructures reveals many interesting patterns that give us clues about their chemical evolution - a process called Galactic archaeology. The lowest metallicity stars that still exist today probably carry the imprint of very few supernova and push Galactic archaeology to its limits. These stars represent our best observational approach to understand the First Stars and the early Galaxy. In this talk I will review cosmological modelling predictions for observations of these very old and metal-poor stars as well as observational efforts and results. In particular, I will present results of the Pristine survey, a Franco-Canadian photometric survey of the Milky Way halo designed to efficiently decompose the metallicity structures of the Milky Way halo. I will show how we can use this great discriminatory power to hunt successfully for the very rare extremely metal-poor stars, to study metal-poor dwarf galaxies, and to search for stellar structures in the halo.

We now know that exoplanets abound in the Galaxy, with most stars hosting at least one planet. These recently discovered worlds are much more diverse than the planets in the Solar System, and raise many questions about their formation, evolution, and habitability. To address these questions, we turn to atmosphere characterization, which provides a wealth of additional information about the planets. I will discuss the state of the art in atmosphere studies, focusing on recent high-precision, space-based observations of hot Jupiters and warm Neptunes. These studies have already revealed planetary atmospheric chemistry, climate, and cloud coverage in unprecedented detail, and they are poised for a revolutionary advance thanks to a series of new and upcoming missions. I will conclude with a discussion of prospects for characterization of temperate, terrestrial worlds with future facilities.

It was always hoped that one day we would be able to use Gaia data to pin down the matter distribution in the Milky Way, measure the Galactic accretion history, find new previously unseen dwarf galaxies with unprecedentedly low surface brightnesses and track narrow stellar streams to gauge masses of Dark Matter sub-halos. I will show that all of these hopes came true with the last year’s Gaia Data Release 2.

We review the status of the Supernova/Gamma-Ray Burst connection. Several pieces of evidence suggest that long duration Gamma-ray Bursts (GRBs) are associated with type Ic Supernovae (SNe). Current estimates of SN and GRB rates show that only a tiny fraction of massive stars, likely less than 2%, are able to produce GRBs. The reasons for this small ratio will be discussed.

Quasars are now thought to have made critical impact on galaxy formation. Feedback from accretion onto supermassive black holes is frequently implicated in establishing the black hole mass vs galaxy bulge correlations and in limiting the maximal mass of galaxies. In this talk, I will review the indirect evidence for quasar feedback as required by galaxy formation models. I will then review the recent progress on detecting direct evidence for quasar-driven outflows and other types of feedback through multi-wavelength observations. These data may provide direct observational evidence for one of the long-standing paradigms in galaxy formation.

Our view of the gas and its physical conditions in the central region of AGN has been enriched by the discover of fast and massive outflows of HI and molecular gas. These outflows can be driven by radiation/winds but also by the interaction of the radio plasma with the ISM. Understanding the origin and quantifying their impact requires to trace their location and derive their physical conditions (density of the gas, mass, mass outflow rate and kinetic energy of the outflow etc.). Particularly interesting has been the finding that in the first phase of their life, jet in radio galaxies can be particularly effective in driving such outflows. This crucial phase is at the heart of the idea of feedback, therefore particularly relevant for studying feedback in action.

In this talk, I will present some of the results we have obtained to trace jet-driven HI and molecular gas outflows down to scales ranging from hundred to tens of pc. The impact of low-power radio jets will be discussed and the comparison with the predictions from numerical simulations will also be presented. Outflows of up to 100 Msun/yr have been found in molecular gas using ALMA while the HI observed with VLBI is showing that the outflowing gas is clumpy as also predicted from numerical simulations. I will describe the kinematics of the gas and its conditions and the relevance they may have for feedback.

For more than 20 years helioseismology, the study of solar oscillations, has provided an exquisite picture of the solar interior structure. However these oscillations, which are standing acoustic waves in the solar interior, have diminishing amplitudes towards the deep interior and render a blurred picture of the solar innermost core, where most nuclear reactions take place and neutrinos are produced. During the last decade, after the discovery of neutrino oscillations, solar neutrino experiments such as SuperKamiokande, SNO and especially Borexino have continued to develop and improve the accuracy and precision of measurements solar neutrino fluxes. Helioseismic and neutrino constraints offer complementary views of solar interiors and open up the best possibilities to date for testing solar (and stellar) evolution theory as well as a laboratory for particle physics.

The talk will first review the current status of (standard) solar modeling in the context of helioseismic constraints, and discuss where problems and uncertainties lie. About the latter, some emphasis will be placed on recent calculations and experiments of radiative opacities that impact solar and stellar modeling. The second part of the talk will present results of solar neutrino experiments, focusing on Borexino's capabilities to perform solar neutrino spectroscopy, and the constraints on solar interior models that can be obtained. The third part of the talk will briefly discuss the relevance of solar model uncertainties for evolution of low mass stars and the uncertainties in determination of stellar properties based on asteroseismic results might be affected. A short final part will include a discussion of the recent claims of detection of gravity modes (g-modes) in solar oscillations.

Star formation takes place in the densest and coldest parts of the interstellar medium (ISM), in dark molecular clouds. These are swept up by multiple supernova explosions on scales of several hundred parsec. While condensing out of the warm ISM, the clouds are continuously fed with fresh gas. Thus, the turbulent substructure and magnetic field properties are imprinted during cloud formation. The formation of dense clouds from the multi-phase ISM, the onset of star formation, and the evolution of the molecular clouds under the impact of stellar feedback from newly born massive stars is studied in high-resolution simulations within the SILCC project. In this talk I will give an overview of the physics and chemistry involved in molecular cloud formation and evolution. After the onset of star formation, the latter is governed by stellar feedback from newly born massive stars. The detailed cloud substructure determines the clouds' vulnerability to stellar feedback processes, in particular to ionizing radiation. Moreover, the ionization state of the gas can be highly variable on scales of tens of parsec due to small-scale turbulent motions within the star-forming clouds, which shield and release the ionizing radiation. This leads to a flickering of the young HII regions on the scale of ~10 pc. On scales of several 100 pc and time scales of tens of Mega-years, the combined feedback from star clusters leads to a reduced star formation rate, such that long depletion time scales are observed.

It has been over 44 years since the last extra-solar X-ray polarization observation was performed. As part of the NASA’s Small Explorer Program a new, exciting mission, will, for the first time, produce image-resolved polarimetry of astronomical sources. I am the Principal Investigator of this mission which includes a significant collaboration with the Italian Space Agency. I shall review the history of astrophysical X-ray polarimetry, discussing various experimental techniques and emphasizing the successful method of tracking the photoelectron in a low-Z gas developed in Italy that has allowed this experiment to proceed. After a discussion of the Observatory and its components, I shall present examples of the scientific advances that can be made by adding imaging polarimetry to the X-ray astronomer’s arsenal of tools for probing diverse questions such as: Was the black hole at the center of the Milky Way galaxy one million times more active a few hundred years ago? What is the spin the black holes in microquasars? Is there direct evidence for the effects of quantum electrodynamics in the strong magnetic fields in magnetars?

The circumgalactic medium (CGM; non-ISM gas within a galaxy virial radius) regulates the gas flows that shape the evolutionary paths of galaxies. It likely contains most of the metals lost in galaxy winds and enough material to sustain star-formation for billions of years.  Owing to the vastly improved capabilities in space-based UV spectroscopy with the installation of HST/COS, observations and simulations of the CGM have emerged as the new frontier of galaxy evolution studies. In this talk, I will describe observational constraints we have placed on the origin and fate of this material by studying the gas kinematics, metallicity and ionization state of gas 10 - 200 kpc from galaxies’ stars. I will conclude by introducing several exciting new techniques for resolving the gaseous structures in the CGM, and by posing unanswered questions about the CGM that will be addressed with future survey data and hydrodynamic simulations in a cosmological context.

Exoplanetary discoveries in the past two decades have unveiled an astonishing diversity in the physical characteristics of exoplanetary systems, including their orbital properties, masses, radii, equilibrium temperatures, and stellar hosts. Exoplanets known today range from gas-giants to nearly Earth-size planets, and some even in the habitable zones of their host stars. Recent advances in exoplanet observations and theoretical methods are now leading to unprecedented constraints on the physicochemical properties of exoplanetary atmospheres, interiors, and their formation conditions.

I will discuss the latest developments and future prospects of this new era of exoplanetary characterization. In particular, I will present some of the latest constraints on atmospheric chemical compositions of exoplanets, made possible by state-of-the-art high-precision observations from space and ground, and their implications for atmospheric processes and formation conditions of exoplanets. The emerging framework for using atmospheric elemental abundance ratios for constraining +the origins and migration pathways of giant exoplanets will be discussed along with their implications for smaller rocky planets. A survey of theoretical and observational directions in the field will be presented along with several open questions on the horizon.

Stellar astrophysics is undergoing a renaissance driven by new observational and theoretical capabilities. Wide-field time-domain surveys have uncovered new classes of stellar explosions, helping to understand how stars evolve and end their lives. Gravitational-wave astronomy is providing exciting insights in the properties of the final remnants of massive stars. Asteroseismology, the study of waves in stars, is also producing dramatic breakthroughs in stellar structure and evolution. Thanks to space astrometry, accurate distances are now available for an unprecedented number of galactic stars. From the theoretical standpoint, it is increasingly possible to study aspects of the three-dimensional structure of stars using targeted numerical simulations. These studies can then be used to develop more accurate models of these physics in one-dimensional stellar evolution codes.

I will review some of the most important results in stellar physics of the last few years, and highlight what are the most relevant puzzles that still need to be solved. I will put particular emphasis on the physics of massive stars, which are the progenitors of core-collapse supernovae, gamma-ray bursts and the massive compact remnants observed by LIGO.