The evolution of interstellar dust reservoirs, and the evolution of galaxies themselves go hand-in-hand, as the presence of dust alters evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust is being formed and altered by processes taking place in galaxies. Indeed, dust can often even be used as a tracer of physical conditions. The exact mineralogical composition, the size and the shape of dust grains, are all affected by the physical conditions. Due to the more permanent nature of solids, dust grains provide a historical record of its processing history, while interstellar gas will only ever probe the present conditions.

I will discuss our recent results on the Magellanic Clouds, Local Group galaxies, the Milky Way, AGN tori, and starburst galaxies, and highlight future observational opportunities open to astronomers to continue the study of interstellar dust in galaxies.

It has been known for decades that the observed number of baryons in the local Universe falls about 30-40% short of the total number of baryons predicted by Big-Bang Nucleosynthesis, inferred by density fluctuations of the Cosmic Microwave Background and seen during the first 2-3 billion years of the universe (redshift z>2-3) in the so called “Lyman-α Forest". While theory provides a reasonable solution to this paradox, by locating the missing baryons in hot and tenuous filamentary gas connecting galaxies, it also sanctions the difficulty of detecting them because they’re by far largest constituent, hydrogen, is mostly ionized and therefore virtually invisible in ordinary signal-to-noise Far-Ultraviolet spectra. Indeed, despite the large observational efforts, only a few marginal claims of detection have been made so far.

Here I will first review the observational efforts pursued over the past 15 years by several groups and will then present our recent results that show that the missing baryons are indeed found in a tenuous warm-hot and moderately enriched medium that traces large concentrations of galaxies and permeates the space between and around them. I will show that the number of OVII systems detected down to the sensitivity threshold of our data, agrees well with numerical simulation predictions for the long-sought hot intergalactic medium, and its detection adds a fundamental tile to the long-standing missing baryon puzzle. Finally, I will comment on the implications of these new results for future high resolution X-ray missions (e.g. Athena).

Cosmic particles at the highest energies travel to Earth from deep space. The questions about their origins and the nature of the acceleration mechanisms that power them to energies much higher than the one reached at the Large Hadron Collider at CERN, have puzzled astronomers for over a century.

On July 12, 2018 the very first association of high energy neutrinos and electromagnetic waves coming from an extra-galactic source has been announced. The association of high energy neutrinos (in total more than 10) back to its origin has revealed the first source of high energy cosmic rays. The source is one of the brightest known blazar, an active galaxy powered by a super massive black hole and characterized by a strong jetted emission pointing towards us.

In this colloquium, the observation of the first source of high energy neutrinos will be reported together with the discussion about future prospective of the field.

The planet-forming region of protoplanetary disks is cold, dense, and therefore weakly ionised. For this reason, MHD turbulence is thought to be mostly absent, and another mechanism has to be found to explain gas accretion. It has been proposed that magnetised winds, launched from the ionised disk surface, could drive accretion in the presence of a large-scale magnetic field. The efficiency and the impact of these winds on the disk structure is still highly uncertain.

In this talk, I will review the most recent development in the modelling of these object, emphasising the role played by magnetised winds on accretion and the formation of large structures. I will show how these models could explain several observed features which cannot be explained by classical turbulent disc models.

Massive stars may have been the first sources of light after the Big Bang.  They are potential contributors to the re-ionization of the Universe and have likely played a crucial role in galaxy formation.  The most massive stars today easily outshine the sun by a factor of a million or more, hence provide strong radiative feedback on their host environment.  Through powerful stellar winds and supernova ejecta they enrich their surroundings with newly processed chemical elements, which constitute the building block of terrestrial planets and life. The recent detection of gravitational waves revealed surprisingly high black hole masses, pointing to very massive progenitor stars in binary systems.

In this talk I will first sketch the role of massive stars in the grand scheme of things. Then, I will focus on aspects of the outcome of the formation of the most massive stars, including maximum formation mass, initial mass function, spin rates and multiplicity properties.  Finally, I will present a possible new insight into the formation mechanism of massive close binaries.

I will describe the numerical efforts to simulate galaxies with the moving-mesh code AREPO across an unprecedented range of halo massses, environments, evolutionary stages and cosmic times. In particular, I will focus on the IllustrisTNG project (www.tng-project.org), a series of three gravity+magnetohydrodynamics cosmological volumes of 50, 100, and 300 Mpc a side, respectively, in a LCDM cosmology. With these, we are capable of both resolving the inner structure of the Universe with thousands among massive groups and clusters of galaxies. I will discuss what is explicitly and empirically solved in gravity+magnetohydrodynamics simulations for galaxy formation in a cosmological context and what is required and what it means to "successfully" reproduce populations of galaxies which resemble the real ones. I will therefore show novel insights allowed by the new simulations, ranging from the assembly of the most massive structures in the Universe to the changes in the star-formation activity and morphological mix of galaxies at early epochs.

With the increasing precision of a wide range of cosmological measurements, tensions are starting to appear in the previously concordant model of Cosmology.  Examples are the discordance between direct measurements of the Hubble expansion rate, and the clustering of dark matter, in comparison to their predicted values from the Planck CMB measurements.

In this talk I’ll review cosmological parameter constraints from the Kilo Degree Survey (KiDS), a now almost complete ESO survey that studies the growth of structures and the expansion history of the Universe using weak gravitational lensing.   As our analysis also finds a low-redshift universe that is in mild tension with the predictions of the Planck CMB experiment, I’ll discuss whether these recent results are our first hint that the Universe is rather more exotic than the standard LambdaCDM model would suggest, or whether this is a sign that new data challenges lie ahead.

The recent 2nd data release of the Gaia mission is revolutionizing our understanding of the Milky Way and its constituents. In this talk, I will highlight a few of the first results stemming from the analysis of this truly spectacular dataset. In particular, I will focus on what we have learned about the dynamics and assembly of the Milky Way and its satellites thus far.

I will review the current theoretical understanding of first stars and black holes and their potential contributions to the Cosmic Infrared Background (CIB). Intriguing indications of the possible emissions from these objects have been obtained from source-subtracted CIB fluctuation measurements using Spitzer/IRAC deep images. The uncovered source-subtracted CIB fluctuations substantially exceed those from remaining known populations. The spatial spectrum of these fluctuations is consistent with populations clustering according to high-z LCDM model. The SED of the CIB fluctuations is blue and consistent with emissions produced by hot objects at high z. Cross-correlation analysis with Chandra X-ray data suggests that the unresolved CIB and CXB are coherent at a remarkably high level implying a fractional abundance of black holes, among the emitters of the CIB, which significantly exceeds that in known populations. I will then discuss an ongoing CIB project, LIBRAE (Looking at Infrared Background Radiation Anisotropies with Euclid), approved by NASA and ESA for the Euclid satellite mission.  LIBRAE will identify the net emissions from the first stars era, lead to a better understanding of the condition of intergalactic medium at that epoch, and, in conjunction with eROSITA, accurately isolate the contributions from the first black holes.

Type Ia supernova are powerful cosmological distance indicators that enable us to measure the expansion history of the Universe. Using SNe Ia distances, scientists discovered the accelerating expansion of the Universe, leading to a Nobel prize and a broad focus on understanding the underlying cause of this acceleration.  SNe Ia distances are also key to measuring the Hubble Constant, the current expansion rate of the Universe and a key cosmological parameter.  Interestingly, the SNe Ia measurements of H0 are ~4 sigma away from the those derived from CMB temperature anisotropy measurements from Planck.  This highly discussed tension could be a sign of new physics, such as a new family of neutrinos.  However, I will discuss how recent studies of SNe Ia in the nearby Universe indicate two separate populations of SNe Ia with different peak luminosities. These differences in the underlying SNe Ia population could introduce a bias in the derived H0 and be the true cause of the tension with CMB measurements.

Over the past 45 years, investigations of ultraviolet absorption features in stellar spectra have revealed that most of the heavy elements in the interstellar medium are depleted from the gas phase to values well below solar or B star reference abundances. The strengths of such depletions reveal the composition of dust grains in space, and they can be characterized by a limited set of empirical parameters that can be linked to the average gas densities and the condensation temperatures of the elements. Two outstanding mysteries remain: one is the fact that the depletion of oxygen exceeds that needed for forming silicates or metallic oxides, and the other is that the chemically inert element krypton shows some depletion. When we observe absorption features in the spectra of quasars to derive the element abundances in foreground intervening galaxies, we can correct for effects of depletions by using the patterns found in our Galaxy or the Small Magellanic Cloud as examples.

The Galactic Center offers the unique possibility to quantitatively test general relativity in the so-far unexplored regime close to a massive black hole. Here we present the latest results from the peri-passage of the star S2 in May 2018. As the star approached the black hole as close as 17 light hours and a speed of almost 8000 km/s, we have followed its orbit with SINFONI spectroscopy and GRAVITY interferometry at the ESO Very Large Telescopes. The GRAVITY instrument, which we have developed specifically for the observations of the Galactic Center black hole and its orbiting stars, is now routinely achieving ~3 milli-arcsec imaging interferometry and with a sensitivity several hundred times better than previous instruments. Its astrometric precision of few ten micro-arcseconds corresponds to only few Schwarzschild radii of Galactic Center massive black hole. The door is now wide open for the quantitative analysis and interpretation of the fundamentals of gravity, all the way from the underlying equivalence principles, to considerations on new physics and their characteristic scales and strengths. The Galactic Center is and will remain the Rosetta-stone for deciphering strong gravity around massive black holes.

The talk will be delivered in two parts.  The first will summarise recent work on searches for any possible space-time variations in fundamental constants. Whilst results to date are suggestive (but inconclusive), the prospects for significantly improving existing measurements are good. We are about half-way through a large survey aimed at making the first 1000 high redshift measurements of the fine structure constant. The target timescale for completion is 2 years.We are also pushing to the highest possible redshifts with a smaller sample of quasars around z=6-7. I will discuss new results from that study.

The second half of the talk will focus on other aspects of cosmological anisotropy. In particular, I will describe a detailed exploration of the statistical properties of the Lyman alpha forest transmission using the SDSS survey. The results are surprising. Huge coherent structures in the HI distribution appear in the data over cosmological scales. The Cosmological Principle appears to reduce to an approximation on scales comparable to the Hubble length.

Using images from Subaru and spectroscopy from Keck, the SLUGGS surveyaims to understand the formation and evolution of massive early-typegalaxies. For a sample of 25 galaxies, we probe the detailedkinematics and metallicities of their field stars to 3-4 effectiveradii and their globular clusters to 8-15 effective radii. From thesedata we have derived 2D maps of the halo stellar kinematics andmetallicity. We find changing kinematic signatures as we probe fromthe galaxy inner to halo regions.  Using JAM models we have derivedthe mass density slope and compare it to the latest cosmologicalsimulations. The SLUGGS survey has also collected over 4000 globularcluster radial velocities (the largest sample to date). From this datawe have derived the dynamical mass and dark matter fractions for ourgalaxies. We compare our results with the latest predictions from theIllustris simulations. We also explore the kinematics and scalingrelations of globular cluster systems. These results are placed in thecontext of two-phase galaxy formation. And if time allows, I willbriefly mention recent work on ultra-diffuse galaxies using the Kecktelescope.

Over the coming decade, our near-infrared spectroscopic view of galaxies and their environments will be greatly expanded with new instruments on the ground and in space. Beforehand, multi-aperture infrared spectrographs on 8-10m class telescopes have already given us a first assessment of the remarkable changes in the intrinsic properties of galaxies up to z ~ 3 as compared to the present day. With respect to our effort, I will give an overview of science results from FMOS-COSMOS, a NIR spectroscopic survey of 1500 emission-line (i.e., star-forming) galaxies at 1.4 < z < 1.7, and over a wide range in stellar mass, with the multi-fiber spectrograph FMOS on Subaru Telescope. Our sample is providing a characterization of the physical properties of the ISM at high-z including the metallicity, pressure, ionization, and dust content. Furthermore, the wide-area coverage of our survey is enabling us to study rare objects (dust-obscured starbursts, AGN), measure the large-scale environments of star-forming galaxies, and estimate the number density of bright Halpha emitters required for planning future cosmological tests. Finally, I will describe plans to further such studies at z > 1 and new science to be achieved with Subaru's Prime-Focus Spectrograph.

The canonical model for the formation of terrestrial planets and giant planets cores relies on an early and very efficient phase of planetesimal growth in a gas-rich circumstellar disk. But, as theorists have known for decades now, there are some formidable obstacles to meeting that requirement, Many of these problems, and potentially their solutions, are associated with the growth, migration and especially the localizes concentration of "pebbles" (mm/cm-sized particles) in the first few million years of a disk's lifetime. That is fortuitous, since continuum emission from these particles in nearby disks can be readily detected and resolved with long-baseline radio interferometers like ALMA. In this talk, I will describe what we are learning about the evolution of solids from such data, including: (1) the signatures of particle growth and migration; and (2) the mounting evidence that small-scale substructures in the (gas) disk play fundamental - and perhaps mandatory - roles in the planet formation process.

The growth of black holes and their role in quenching massive galaxies is a key unsolved problem in galaxy formation. I present a new suite of cosmological hydrodynamic simulations called Simba, which builds on our successful Mufasa simulations to include a novel torque-limited black hole accretion model and AGN feedback using observationally-constrained bipolar kinetic jets. I will describe the physical motivations behind our new model, explain why they represent an improvement over other current black hole growth and feedback models, and demonstrate that they yield a galaxy population in very good agreement with numerous observations across cosmic time. These successes set the stage for exploring galaxy--black hole co-evolution towards better understanding the impact of AGN feedback on the baryon cycle along the mass hierarchy.

Measurements of the CMB have driven our understanding of the universe and the physics that govern its evolution from primordial quantum fluctuations to its present state. They provide the foundation for the remarkable 6-parameter cosmological model, ΛCDM, which fits all cosmological data, although there are some tensions, which may provide hints at new physics. Far from being the last word in cosmology, the model raises deep questions: Is Inflation correct? What is its energy scale? What is the dark matter? What is the nature of dark energy? Are there additional light relic particles? The increasingly sensitive CMB observations being made to address these questions also provide powerful and unique probes of astrophysics. This talk will discuss recent experimental developments and observational results, primarily from the 10m South Pole Telescope (SPT), as well as the vision and planning for future CMB measurements, in particular CMB-S4.

In this talk, I will present my work on two novel ways to map the Galaxy. The first one exploits a particular class of dark matter tracers - hypervelocity stars. These are stars observed in the halo with trajectories consistent with coming from the Galactic. My group has undertaken a comprehensive program to find them in the Gaia catalogue and model them in a full statistical framework to extract information on the mass and the shape of the Milky Way's halo. In addition, we are forecasting the ability of double white dwarfs to trace the Milky Way bulge and disc, when combining Gaia and LSST data with the future gravitational wave detections by the ESA mission LISA.

In the last decade a large effort has been dedicated to detect one of the last phase transitions in the Universe called the Epoch of Reionization and its preceding epoch know as the Cosmic Dawn, specially with the redshifted 21 cm probe. I will review the status of the various constraints that we currently have on reionization. I will also show the current results from a number of operating telescopes in the 2 meter wavelenght, a special attention will be paid to the recent results obtained from telescopes like EDGES and LOFAR.

The centers of massive galaxies are special in many ways, not least because all of them are believed to host supermassive black holes. Since the discovery of a number of relations linking the mass of this central black hole to the large scale properties of the surrounding galaxy bulge it has been suspected that the growth of the central black hole is intimately connected to the evolution of its host galaxy. However, at lower masses, and especially for bulgeless galaxies, the situation is much less clear. Interestingly, these galaxies often host massive star clusters at their centers, and unlike black holes, these nuclear star clusters provide a visible record of the accretion of stars and gas into the nucleus. I will present our ongoing observing programme of the nearest nuclear star clusters, including the one in our Milky Way. Theses observations provide important information on the formation mechanism of nuclear star clusters. They allow us to measure potential black hole masses and might give a clue on how black holes get to the centers of galaxies.

The detection of gravitational waves has opened a new era of scientific discovery, as it permits a new kind of observation of the cosmos, quite different from electromagnetic and particle observations. In this talk I will review the gravitational-wave signals detected up to now by LIGO and Virgo, and discuss the theoretical groundwork that allows to identify and interpret those signals. I will also highlight how those new astronomical messengers are unveiling the properties of the most extreme astrophysical objects in the universe and probe fundamental physics.

Stellar spectroscopy is becoming vitally important in many fields of modern astronomy. This method allows estimation of fundamental parameters of stars and their chemical abundances, the information crucial for studies of stellar physics, star - planet connection, structure and evolution of galaxies. Large surveys, like the Gaia-ESO and 4MOST, will deliver millions of spectra of stars from the most distant corners of the Milky Way. Next-generation facilities, like the E-ELT, will observe stars beyond tens of megaparsecs past the Local Group.

I will highlight some of the key advances in spectroscopy of cool stars, both from the observational and theoretical perspectives. New models of stellar atmospheres and spectra, which account for hydrodynamics and non-local thermodynamic equilibrium, make stars look different and turn classical concepts about stellar physics and Galactic  evolution upside-down. I will discuss how these developments impact our understanding of the Milky Way’s past, in particular, in relation to the emerging field of Galactoseimology, and present outlook for the future studies.

Extragalactic astrophysics suffers from an extreme case of time scale mismatch between human lives (1e2 years) and galaxies (1e8-9 years), making laboratory experiments impractical. In order to build a physics-based account of how galaxies formed and evolved together with their central supermassive black holes, we need to be able to forward model the processes involved.

I will present the ways in which my group attempts to do this using a combination of phenomenological models and artificial intelligence. I discuss how a large fraction of the behavior of black holes can be accounted for with a simple, near-universal distribution of accretion rates originating very close to the black hole, and how this fits into our understanding of how galaxies `turn off' their star formation. I also show how we can use new methods from artificial intelligence to extract more insight from existing data, and how we can use the for data-driven forward models of galaxy evolution. Finally, I outline how data-driven methods can push forward astrophysics in particular and science in general over the coming years.

The evolution of the star formation activity and, thus, the assembly of the stellar content of galaxies remain at the heart of galaxy evolution studies. It is now rather well established that most galaxies form stars at a level, dictated mainly by their stellar mass and regulated by secular processes. This is seen as a Main Sequence (MS) in the Star `Formation Rate (SFR)-stellar mass plane. The normalization of this sequence declines with time since z~2, indicating an overall decrease of the star formation activity of the galaxy population in the Universe. However, we do not yet fully understand the processes that control this evolution, nor how individual galaxies evolve relative to it. While the existence of a MS may seem to suggest a simple and universal mode of star formation in galaxies (on average), the deviations indicate a more complex relation between galaxy SFRs, gas reservoir, external and internal mechanisms triggering or halting star formation. In this context I will show, with a statistical approach, how the MS evolves from the local Universe up to z~2 in slope and normalization, by using the deepest available UV and far-infrared galaxy surveys. In addition, I will discuss our results based on the Hubble Deep UV (HDUV) Survey about the interplay between environment, morphology and feedback in setting the distribution of galaxies around the MS at any redshift.

The composition of cometary ices provides clues to the chemistry and conditions prevailing in theearly solar system. Since the detection of HCN at millimeter wavelengths in comet C/1973 E1 (Kohoutek), almost 30 molecules have been identified in cometary atmospheres from remote sensing observations from ground or from space platforms. Thanks to progresses in instrumentation and the availability of large telescopes, complex organic molecules have been identified. Measurements will be reviewed and the observed chemical diversity among comets will be presented. The relative abundances will be compared to values measured in star-forming regions to discuss the possible formation routes of cometary molecules. The talk will also include new findings about comet composition obtained from the Rosetta mission to comet 67P/Churyumov-Gerasimenko.

Understanding the physics of galaxy formation is an outstanding problem in modern astrophysics.

Recent cosmological simulations have demonstrated that feedback by star formation, supernovae and active galactic nuclei appears to be critical in obtaining realistic disk galaxies and to slow down star formation to the small observed rates. However in particular physical processes underlying these feedback processes still remain elusive. In particular, these simulations neglected magnetic fields and relativistic particle populations (so-called cosmic rays). Those are known to provide a pressure support comparable to the thermal gas in our Galaxy and couple dynamically and thermally to the gas, which seriously questions their neglect.

After introducing the underlying physical concepts, I will present our recent efforts to model cosmic ray physics in galaxy formation. I will demonstrate that cosmic rays play a decisive role on all scales relevant for the formation of galaxies, from individual supernova remnants up to scales relevant for entire galaxies and even galaxy clusters.

Deriving accurate ages of stars is one of the most important, if elusive, goals of modern-day astrophysics.

In this talk, I will review some of the techniques that have been used to infer such ages, with emphasis on the oldest stars. Recent applications to stellar clusters and field stars alike will be critically discussed, as will the implications of this work for different areas of astrophysics.

Understanding the evolution of baryonic mass at the centers of clusters is critical if we are to form a consensus on the evolution of structure. I will argue that while the growth and properties of Brightest Cluster Galaxies are becoming better understood through a range of surveys, the growth of the (hard-to-detect) intra-cluster light (ICL) is currently poorly constrained, despite the fact that the ICL makes up a significant fraction of the photospheric light in clusters. I will look at some of the challenges to ICL work using existing public survey pipelines, including HSC, and the techniques we have developed to overcome them. Finally, I will take a brief look at the prospects of similar science with the Large Synoptic Survey Telescope (LSST). With its unique combination of depth (five magnitudes deeper than SDSS) and area (20,000deg^2) LSST can reveal assembly histories of galaxies and the ICL with appropriate sky estimation techniques.

Neutron stars are compact remnants of supernova explosions. They have radii of 10-15 km and masses comparable to that of the sun. One could expect neutron stars to be quiet, dead remnants of stellar evolution. Instead,they happen to produce most spectacular, extreme radiative phenomena. This talk will give a broad overview of neutron star activities and recent progress in understanding their mechanisms. Neutron stars generate powerful beams of coherent radio waves, pulsed high-energy gamma-rays, relativistic electron-positron winds, and giant X-ray flares. Some neutron stars live in binary systems and eventually merge, emitting strong gravitational waves and creating explosions observed from cosmological distances. Recent observational discoveries will be discussed, including the exciting detection of gravitational waves from a neutron star merger and its electromagnetic counterpart.