Seminars and Colloquia at ESO Garching and on the campus

Measurements of the extragalactic background light in the 1990s revealed that nearly half of all starlight in the Universe is absorbed by dust and re-radiated into the far-infrared. In the decades since, we have come to understand the importance of this dust-obscured mode of star formation, which has dominated the volume-averaged star formation rate density over the unobscured mode for the past 12 billion years. The submillimeter-bright population of dusty star-forming galaxies (DSFGs) contributes substantially, with prodigious assembly of stellar mass at rates of 100-1000+ Msun per year. With telescopes like ALMA and JWST, we can resolve their internal structure for the first time. A large fraction of these extreme objects are well-described as isolated rotating disks that replenish gas continuously from the surrounding circumgalactic medium, suggesting that many are simply the highest-mass end of the star-forming main sequence of galaxies. Their ability to sustain intense, efficient star formation is reshaping our conception of how stellar feedback regulates galaxy growth in the early Universe. I will discuss in particular how gravitational lensing is a key tool for zooming in on critical ~100 pc scale regions. Finally, in the latter part of my talk, I will introduce SN-ECHOES, an upcoming JWST Cycle 5 program designed to search for lensed supernovae in DSFGs and their nearby companions with multi-epoch NIRCam imaging. This program has the potential to discover new candidate supernovae for inferring the Hubble constant, H0, through a technique known as time-delay cosmography, but it will also provide a valuable opportunity to better understand the Mpc-scale environments of extreme DSFGs.

The Extremely Large Telescope (ELT) is set to transform ground-based astronomy in the 2030s. Yet the scientific return of even the largest telescope ultimately depends on the capabilities of its instruments. The ANDES spectrograph will serve as the ELT’s high-resolution spectrograph, operating across optical and near-infrared wavelengths. Its science goals span some of the most compelling questions in modern astrophysics: detecting biosignatures in the atmospheres of rocky exoplanets, uncovering the chemical fingerprints of the first generation of stars, and testing the stability of Nature’s fundamental constants.

How do such ambitious objectives translate into a working instrument? This informal discussion will explore how cutting-edge astronomical instruments are conceived, designed, and built, and the role ESO plays in bringing them to life.

Despite the key role of the large-scale matter distribution in the Universe in regulating hierarchical structure formation, its impact on the baryonic physics that shape star formation and chemical enrichment histories of galaxies is still not fully understood. In this work, we assess the effect of local and large-scale environmental metrics on stellar population properties and star formation timescales derived from rest-frame optical absorption spectra and photometry of massive LEGA-C galaxies at 0.6<z<1. We report that overdensity derived from reconstructed density field is the main environmental metric driving the stellar population properties of massive galaxies (M_star>10^10 Msun) at intermediate redshifts. We observe that galaxies of a given stellar mass in overdense regions are older and form earlier on and over shorter time-scales than the ones in underdense regions. What’s more interesting, these trends remain after accounting for the galaxies’ hierarchy within groups and clusters and their position in the large-scale cosmic web. Our results suggest that the initial conditions of the matter density field have a profound effect on the quenching and star formation histories of galaxies, leaving an imprint into observed galaxy stellar populations and scaling relations that are already in place at intermediate redshifts.

Spirals are iconic features of galaxies, and yet conventional theoretical models for how they emerge and evolve only partially capture their observed traits and their connections to their host disks.  Recent JWST observations of beautiful, regular spiral patterns at redshifts z~2 and beyond underscore the need to resolve these theoretical shortcomings.  I will present a new picture of spiral patterns as short-lived density waves, analytically bridging the gap between the conventional long-lived density wave picture and the model of spirals as transient material patterns.  This new view forces a wholesale revisioning of how spirals influence their host galaxies: rather than merely reflecting conditions in the underlying disk, collectively excited spirals actively shape it, producing widespread changes in galaxy structure through dynamical heating and changes in angular momentum.  I will describe how these widespread changes are the very ingredients that give rise to global spiral patterns and naturally lead to stellar bulge growth, radial gas inflows and an overall structural compaction over cosmic time.  The picture of global, collective spiral excitation also has implications for the kinematics and the rich structure of gas disks, as revealed by JWST/MIRI imaging of nearby galaxies. These structures suggest a simple unified model in which radial gas flows appear alongside dynamical heating, and the latter acts as an important source of turbulent motion to offset dissipation.

Less than 30 years ago, we did not know whether planets exist outside our solar system. Fast forward to 2026, astronomers have discovered well over 7000 planets orbiting other stars similar to our Sun, including some that may have the right conditions to host life. As we learned that the formation of planets seems to go hand-in-hand with the birth of stars, we begin to wonder:

• What happens to planetary systems when their host stars run out of fuel, and turn into Earth-sized white dwarfs?
• Are those systems, if they exist, detectable?
• What will happen to our solar system, and to the Earth?
• And what are the possible implications for life?

I will discuss the final fate of planetary systems, the observational fingerprints of planets and their debris orbiting white dwarfs, and how studying these exotic systems help us to improve our general understanding of the formation of planets.

White dwarfs are at the core of several research areas in modern astrophysics: one of the dominant low-frequency gravitational wave signals that LISA will detect originates from the galactic population of short-period white dwarf binaries; white dwarf binaries are also the progenitors of thermonuclear supernovae (the cosmic beacons that led to the discovery of dark energy); and white dwarfs are also excellent laboratories to study accretion physics. I will give an overview of our observational census of the extremely varied population of white dwarf binaries, and of our theoretical understanding of their evolution.