Seminars and Colloquia at ESO Garching and on the campus

The interpretation of stellar surface images, fundamental parameters, stellar variability, and the detection and characterization of hosted planets requires realistic simulations of stellar convection. Regarding exoplanetary atmospheres, a time-dependent representation of the background stellar disk using 3D radiative-hydrodynamical (RHD) simulations is a natural and necessary step toward a better understanding of stellar properties and enabling a detailed and quantitative analysis of the atmospheric signatures of hosted planets. 3D RHD simulations have been, and will continue to be, crucial for studying the properties and dynamics of evolved stars as well. I will present how these simulations and their observables extend across the M-type domain of the Hertzsprung–Russell diagram.

We used ALMA for what it was built for: opening up new science by observing in the high frequency Band 10 (and 9). Specifically, we targeted the [OI] 63µm fine structure line in a sample of 12 gravitationally lensed dusty star-forming galaxies at 4.2<z<5.8. This line was expected to be as bright as the [CII] and [OIII]88µm lines, but we found it to be almost 100x fainter. Such extreme line ratios can only be explained by very strong self-absorption by foreground material within the galaxies, as also predicted in new hydrodynamical simulations. We only detect several narrow, spatially localized  [OI] 63µm emission “escape channels” preferentially detected in regions with weak or absent dust continuum emission. Intriguingly, in a few cases, the [OI] 63µm is detected in absorption against a bright continuum, reaching levels below the local CMB temperature. This suggests the presence of low-excitation, low-density gas along the line of sight. We argue that the very high [OI] 63µm optical depth is the dominant effect causing this strong absorption, limiting the diagnostic power of this line to trace regions of massive start formation in high-redshift DSFGs.

Unraveling the planet formation process and the origin of the diversity of planetary systems require a comprehensive understanding of the planet-forming disks surrounding young stars. ALMA’s unprecedented spatial resolution and sensitivity have enabled a detailed examination of the physical and chemical structures of planet-forming disks (at ~10 au scale). The detections of gaps and rings in numerous disks have transformed our understanding of disk evolution and planet formation. I will first provide a summary on the detection and characterization of disk substructures, and discuss the exciting avenue of young planet search as guided by these disk features. While ALMA excels in probing the bulk disk property, the very innermost disk (within 1-3 au), remains elusive to its capabilities, which can now be well studied with JWST. In the second half of the talk, I will touch upon our expanding view of the inner disk chemistry, especially the interplay with substructures at large disk radii and for disks around very low-mass stars. By leveraging the capabilities of ALMA and JWST, we aim at establishing a global view of disk evolution, laying the groundwork for the development of a robust predictive model of planet formation.  

Bio: Feng Long is an Assistant Professor at the Kavli Institute for Astronomy and Astrophysics of Peking University. After receiving her PhD from Peking University in 2019, she spent three years as an SMA Postdoc Fellow at the Center for Astrophysics | Harvard & Smithsonian. From 2022 to 2025, she worked at the University of Arizona as a NASA Sagan Fellow. Her research uses advanced facilities like ALMA and JWST to study protoplanetary disk evolution and planet formation. 

Asymptotic Giant Branch (AGB) stars play a key role in galaxy evolution 

by producing dust and enriching the ISM. Moreover, during their 

thermally pulsing (TP-AGB) phase, they can contribute up to 50% of the 

integrated NIR light in galaxies with stellar ages between 0.2 and 2 

Gyr. Accurately modeling the TP-AGB phase is therefore essential for 

reliable SED-based estimates of stellar ages, masses, metallicities, 

dust attenuation, and photometric redshifts. This will become even more 

relevant for galaxy evolution studies using upcoming deep, wide-area 

surveys such as Euclid and LSST. However, the TP-AGB phase is 

notoriously difficult to model, leading to uncertain lifetimes and NIR 

luminosities, and previous small-sample studies reported contradictory 

results. We address this remaining uncertainty using ultra-deep 

JWST-NIRspec spectra of a sample of 10 z~0.7 quiescent galaxies, 

combined with a systematic analysis of a much larger quiescent galaxy 

sample based on LEGA-C spectra and COSMOS-Web photometry. In this talk, 

I will present our measurements of the TP-AGB contribution to the NIR as 

a function of stellar age and metallicity and discuss the implications 

for galaxy evolution.

When governments decide whether to invest in long-term international research infrastructures such as ESO, what factors shape their decisions? Is scientific excellence sufficient? What additional returns do Member States expect?
As part of my role, I report regularly to ESO’s Member States on the national impact and benefits of membership. While scientific leadership and discovery remain integral, they represent only part of the value proposition that governments evaluate.
I will speak on the broader framework within which governments assess participation in large-scale astronomy organisations. How expectations have evolved, the role of science diplomacy in decision making, and the role of astronomers in the long-term organisational sustainability for ESO.

Outflows driven by the propagation of radio jets in galaxies used to be so rare that they were thought of as oddities. Thanks to ALMA, instruments on the VLT, and JWST, jet-driven outflows are now routinely detected in the local and distant Universe. They are even used to indicate the passage of jets they have outlived, which can no longer be detected at radio wavelengths. The molecular gas in such outflows is heated, excited, and often dispersed, becoming optically thin. Yet, very dense cores are also found within the flow. I will summarize findings on the properties of the gas in jet-induced molecular outflows, and I will address how we can link them to ongoing star formation changes. For this purpose, I will present a stability analysis for entrained clouds, performed with the aid of data from all the above-mentioned facilities and excitation/radiative transfer codes that provide the multi-phase gas pressure.

Over the past decade, observations of protoplanetary disks have revealed numerous substructures in their dust distributions at both (sub)millimeter and near-infrared (NIR) wavelengths. These features provide a blueprint for the wide range of physical properties and orbital architectures observed in exoplanetary systems. Although the origins of these disk substructures remain uncertain, their multiplicity reflects the underlying gas dynamics, as dust grains are coupled to gas motion. By examining the motion of gas within these disks, we can investigate the physical processes that govern disk evolution and planet formation. In this talk, I will present an overview of recent and upcoming science results from the exoALMA Large Program, a sub-millimeter planet-hunting campaign that employs molecular line observations to uncover the complex gas kinematics of protoplanetary disks.

The recently launched XRISM (JAXA/NASA/ESA) observatory has provided long-awaited high-resolution spectra of extended X-ray sources, including clusters of galaxies. These spectra enable direct measurements of gas kinematics in the intracluster medium (ICM). I will present XRISM results from observations of well-known bright galaxy clusters and discuss their implications for the physics of AGN feedback, ICM turbulence, cluster mergers and their assembly history, and cluster mass measurements for cosmology. Finally, I will compare these measurements with cosmological simulations, highlighting both what they reproduce and remaining challenges.

The SDSS-V Local Volume Mapper is a novel integral field spectrograph with an extremely wide field of view. It is currently conducting a survey of a large fraction of the Southern Milky Way plane and the Magellanic Clouds.
In this talk I will present the results of Early Science observations which target the massive globular cluster Omega Centauri.
Due to its brightness and large extent in the sky, this cluster provides a perfect benchmarking target for extragalactic stellar population studies. At the same time the wide LVM field of view allows study of the poorly constrained kinematics in the outer region of the cluster, providing a missing piece for dynamical modelling efforts.

From the integrated light we successfully measure the rotation curve of the cluster out to a radius of three half-light radii, significantly extending the range of our previous kinematic investigations based on resolved measurements with VLT MUSE. We can also recover the age and the metallicity of the cluster and provide detailed comparisons between different single stellar population models.

Thanks to the Hubble Space Telescope, combined with major ground-based facilities and gravitational lensing (“cosmic telescopes”), we have entered an era in which stellar clusters can be identified at cosmological distances. The James Webb Space Telescope (JWST) is now transforming this field -- and, more broadly, our view of the early Universe. With its exceptional sensitivity and angular resolution at infrared wavelengths, JWST, when coupled to strong gravitational lensing, can isolate individual star clusters even within the first half 0.5 Gyr of cosmic history. This lensing-enhanced spatial contrast enables the identification of candidate progenitors of present-day globular clusters and places them in the context of key questions, from the sources of ionizing photons during reionization to the emergence of extremely metal-poor (possibly near-pristine) star formation, and the possible connection to black-hole seeds. Looking ahead, ground-based facilities in the 2030s equipped with extreme adaptive optics (AO) -- most notably the ELT -- will consolidate these studies and push to even finer physical scales. The synergy between space and ground-based facilities will thus open an unprecedented window on the earliest stellar systems, connecting parsec-scale star formation to the assembly of galaxies and black holes in the reionization era.

Red supergiant stars (RSG) are experiencing significant mass loss. It ultimately determines their late evolution into a type II supernova leading to a remnant that can be a neutron star or a black hole. Therefore, understanding the mass loss properties is key to predicting their final fate. Optical interferometry has previously shown that the surface of RSGs present prominent convective features. Further away from the photosphere, several direct images of RSG have revealed large clumps of dust in their surroundings, providing clear evidence of inhomogeneous mass loss. However, current radiative-hydrodynamics simulations of RSG fail to explain how such an amount of material leaves the star, although they do predict the strong convective activity. Antares, the closest RSG, is the ideal laboratory to better investigate the mass-loss phenomenon, its triggering mechanisms, and the processes by which material escapes from the star. Using a multi-epoch VLTI/GRAVITY dataset, we aim to link the convection on the star’s photosphere to the material in the upper molecular layers, and ultimately unveil the physical mechanism that triggers mass loss.

I will present an overview of the instrumentation development program and strategic R&D interests of the Herzberg Astronomy and Astrophysics Research Center, part of the National Research Council of Canada. Active major facility class instrumentation development includes real time control systems for the ELT's ANDES and MORFEO  instruments, next generation correlators for ALMA and the SKA mid telescopes, opto-mechanical systems for the Gemini Infrared Multi-Object Spectrograph (GIRMOS) and the second generation of the Gemini Planet Imager (GPI2), as well as low noise amplifiers for SKA mid and CCAT. I discuss the related R&D program and technology development roadmaps, including but not limited to adaptive optics, high contrast imaging and detectors. Finally, I discuss the evolving Canadian astronomical landscape and highlight future opportunities.

Understanding how atmospheres move is key to understanding the inner workings of planets - how their material is distributed and the subsequent implications on their formation and potential to host life. In our own Solar System, the observable fingerprints of winds in spectra are easily accessible and have provided substantial input into the composition and formation of our gas giants. Until recently, however, directly measuring winds in exoplanet atmospheres remained out of reach.

In this talk, I will present recent results that use ESPRESSO in 4-UT mode to directly probe atmospheric winds on close-in exoplanets. By resolving individual atomic absorption lines during planetary transit, we can detect Doppler shifts caused by day-to-night flows and global circulation patterns at different depths in these distant worlds. These measurements provide the first direct three dimensional constraints on wind speeds and directions in exoplanet atmospheres.

I will outline the observational technique, discuss what these wind measurements tell us about atmospheric dynamics and energy transport under extreme irradiation, and highlight how such observations are opening a new window on comparative planetology beyond the Solar System — just in time for the ELT era.

James Webb Space Telescope (JWST) has opened a new window into the early universe, enabling sensitive, high-resolution images of the near-infrared sky and spectroscopy of faint, distant sources. The JWST Advanced Deep Extragalactic Survey (JADES) is a collaboration of the NIRCam and NIRSpec GTO teams pooling over 750 hours of JWST time to conduct an ambitious study of galaxy evolution in the Great Observatories Origins Deep Survey GOODS-South and GOODS-North fields. I will discuss exciting results from JADES observations about discoveries in the distant (z>12!) universe that provide new insight into the process of early galaxy formation and cosmic reionization. We discuss how our new constraints on star formation and galaxy growth at the very earliest times are rewriting the story of how the first galaxies form and evolve.

One of the most surprising results coming out of the first years of science operations with JWST is the unexpectedly high abundance of actively accreting black holes in the early Universe. Compared to the local population, many of these early black holes appear to differ in various aspects, such as their relation to their host galaxies or their multi-wavelength properties. These observational findings challenge our understanding of the past evolution of present-day supermassive black holes, and provide new ways to constrain theoretical models of black hole formation and growth. I will give an overview of recent observational results on massive black holes in the first few billion years, driven by the unprecedented capabilities of JWST to explore cosmic dawn, and with a focus on results from the GTO and GO NIRSpec-IFS surveys GA-NIFS and BlackTHUNDER.

Combining telescopes (or antenna) has been a staple of observatory design and operations. The technique, known as interferometry, is rooted in the nature of the light we are seeking to observe: because of light’s wave nature, interferometry provides high angular resolution without having to build prohibitively large collecting areas. Our own Very Large Telescope Interferometer (VLTI) is one of the very few interferometers operating in the optical regime, and arguably the most ambitious one with the largest telescopes, most advanced adaptive optics and laser guide stars.

The recent first light of the 4 UTs with laser guide stars is an opportunity to retell the story of VLTI, which started in the late 1970’s with extraordinary scientific vision and perceptive technical foresight. What kind of observations are carried out by VLTI? how unique are its contributions? What will the recent upgrade (GRAVITY+) yield? After introducing a brief history of the VLTI (and the VLT), I will showcase the recent and prospective astrophysical results of this unique facility.

An Informal Discussion showcasing the analysis of Chen et al. 2025, “Who Uses Whose Telescopes? Analyzing the Knowledge Geography and Research Dominance of Global Astronomical Facilities”, sparked curiosity about the initiatives ESO has supported in Chile (its hosting country) regarding scientific and technological advancement. Since 1995, ESO has committed to supporting the development of astronomy in Chile, in the form of direct funding for research, education and training. We will show the main legal basis of the involvement of ESO in the development of astronomy in Chile, based on the “Acuerdo” for the construction of telescopes and its further modifications. Then, we will discuss the variety of astronomy initiatives supported by ESO, with an emphasis on the projects financed by the “Comite Mixto ESO-Chile", including its regional call, and the participation of Chilean students and postdocs in ESO programs.

Distinct sets of elements are produced from different nucleosynthesis processes in galaxies that occur in core-collapse supernovae (CCSNe), Type-Ia supernovae (SNe Ia), asymptotic-giant-branch stars (AGBs), and various other enrichment sources. I will discuss both supernova and AGB enrichment in galaxies, as probed from integrated deep emission-line spectra of star-forming galaxies (SFGs) with direct elemental abundances. Galactic chemical enrichment from SNe has historically been constrained by alpha-enrichment ([α/Fe]) and metallicity ([Fe/H]) measurements from deep absorption-line spectra of individual stars in the Milky Way (MW) and some local group dwarf galaxies (and a handful of massive ellipticals with deep integrated absorption-line spectra out to z~2). The vast majority of galaxies in the universe are SFGs, with their fraction increasing with increasing redshift. We have recently shown that for SFGs (having deep integrated spectra with temperature sensitive auroral lines, enabling direct abundance determination), the oxygen-to-argon abundance ratio, log(O/Ar), vs Ar abundance, 12+log(Ar/H), is analogous to [α/Fe] vs [Fe/H] for stars. At low-z (z<0.3) with SDSS observations of ~800 SFGs, we show that galaxy chemical enrichment history is driven primarily by the interplay of CCSNe and SNe Ia, with their impact varying with galaxy mass. With a smaller sample of 11 SFGs at high-z (z~1.3-7.7) with JWST/NIRSPEC and Keck/MOSFIRE, we show that MW-like CCSNe and SNe Ia dominated enrichment processes occur at least out to z~4, beyond which rapid but intermittent star-formation may be at play. On the other hand, AGB nucleosynthesis is probed in SFGs from relative abundances of N & O. NIRSPEC@JWST observations revealed a handful of SFGs at high-z with high N/O abundance ratio at low O/H, dubbed extreme N-emitters. Some attribute this to extreme enrichment mechanisms active only in the early universe. However, we found high N/O at low O/H for a sample of 19 low-z (z<0.5) SFGs (a five-fold increase compared to earlier) using DESI DR1 spectra. The enhanced N/O values can be explained using galactic chemical evolution (GCE) models having long-lived N-enhancement from AGBs, coupled with strong outflows.

I will discuss the results from my recent research that explores multi-phase gas reservoirs in extreme environments during the epoch of peak cosmic star formation (z ~ 2-4). Using multiwavelength observations, we reveal how massive gas structures fuel intense star formation in overdense regions while being shaped by energetic feedback processes. Our work demonstrates that both high-resolution interferometry and wide-field observations are essential for understanding the complete picture of gas as protoclusters begin to take shape.

High-resolution data resolve compact cores with extraordinary star formation rates and reveal narrow metal-enriched filaments tracing galactic outflows extending 60+ kpc from their hosts. Meanwhile, single-dish observations recover a significant excess of gas than interferometric maps alone, revealing extended low-surface-brightness reservoirs that could represent a proto-intracluster medium. Together, these findings reveal complex gas ecosystems in the early universe where intense star formation, AGN activity, and powerful feedback coexist, driving the assembly of the most massive cosmic structures.

Understanding the role of magnetic fields in the formation of planetary systems has been a long-standing goal of astronomy. Although magnetic fields are widely believed to be a critical ingredient in planet formation, direct observational constraints during the protoplanetary disk phase remain limited. In this talk, I will review previous efforts to detect magnetic fields threading protoplanetary disks and discuss the key limitations of these approaches. I will then present a new observational technique that we have recently developed, which enables a more robust detection of disk magnetic fields. Finally, I will place these results in the broader context of Solar System constraints and outline how forthcoming observations and planned upgrades to ALMA will further advance this field.

NASA has invited the ADS team to further expand to other Earth and space science disciplines. Thus, SciX was born as a new service built on top of ADS infrastructure and databases. By serving a broader range of disciplines, SciX will also foster cross-disciplinary discovery. In this Informal Discussion, I will provide an overview of the current situation, ADS’ way forward, and present SciX. Particular emphasis will be put on how researchers can use SciX effectively with minimal changes to their established workflows.

Faint blazars are often difficult to identify, as their recognition typically requires cross-matching positional counterparts across radio, optical, and X-ray catalogs. To support high-energy studies for the Cherenkov Telescope Array Observatory (CTAO), we adopted an alternative approach. Starting from the Fermi-LAT 4FGL-DR4 catalog (5,062 γ-ray sources at galactic latitude |b| > 10°), we searched for blazar counterparts using Firmamento*, a web-based platform developed within the Open Universe initiative of UNOOSA. Firmamento integrates multi-frequency data and high-level analysis tools for spectral energy distribution (SED) studies.
By combining automated algorithms with visual inspection and validation by experts, high-school, and undergraduate students — given the large size of the sample — we discovered 421 new blazar associations, reducing the fraction of unassociated Fermi-LAT sources from 25% to 17%. The resulting catalog, 1FLAT, has been published in the Astrophysical Journal Supplement Series.
This talk presents both the scientific results and the educational framework behind this collaborative effort.

 

* https://firmamento.nyuad.nyu.edu/data_access