Seminars and Colloquia at ESO Santiago

Low-mass galaxy groups are the most common environments for galaxies and serve as a key bridge between cosmological structure formation and galaxy evolution. Yet, their hot gas and baryonic content remain poorly characterized, largely due to their low surface brightness in X-rays. In this talk, I will show how spectral stacking of eROSITA data offers a powerful method to uncover the X-ray properties of galaxy groups and clusters identified through large spectroscopic surveys, including SDSS, GAMA, and DESI. Focusing on eRASS1 results, I will present stacked X-ray measurements for these systems and compare them with mock observations based on hydrodynamical simulations such as Magneticum and IllustrisTNG. This technique allows us to trace the intra-group medium from massive clusters down to group scales comparable to the Local Group, extending and validating key X-ray scaling relations into the low-mass regime. These results open new pathways to connecting observations and theory across the full mass spectrum of cosmic structures

Quasar studies with Herschel/SPIRE often report host luminosities ranging from 10^{12} to 10^{14} solar luminosities, suggestive of star formation rates (SFRs) of up to several thousand solar masses per year. However, due to the limited spatial resolution of SPIRE, it is uncertain whether the far-infrared (FIR) emission originates from the quasar itself, nearby sources, or unrelated sources within the SPIRE beam. High-resolution observations at wavelengths close to the SPIRE coverage are needed to pinpoint the true source of the FIR emission. In this talk, I will discuss the unambiguous identification of ALMA Band 7 counterparts of a statistical sample of 152 FIR-bright SDSS quasars and subsequent multiplicity rates among these systems. The multiplicities will be discussed as a function of redshift, IR properties and "balnicity". I will also report on the serendipitous detection of intermediate CO transitions. Preliminary results on the SEDs of these objects and the calibrated SFRs will also be shown.

Galaxy clusters exhibit Mpc-scale diffuse radio emission that is associated with the microphysics of the intracluster medium (ICM) and with radio galaxies. However, many questions remain open regarding the origin of this diffuse radio emission. In this talk, I will discuss the role of AGN bursts, merger shocks, and particle acceleration mechanisms, such as diffusive shock acceleration (DSA) and turbulent re-acceleration, in explaining radio observations. I will present results from MHD simulations of binary galaxy cluster mergers that include a jet model injecting a bi-directional, cosmic-ray (CR)–loaded jet at the center of the main cluster. I will discuss the role of sloshing, turbulence, and shocks in redistributing CRs from central AGN throughout galaxy clusters. Finally, if time allows, I will present preliminary results based on simulations and LOFAR radio observations of the cluster MACS J0018.5+1626, highlighting the power of combining multi-wavelength analyses with simulations of individual systems to better constrain the underlying merger and ICM physics.

For the 11th International Day of Women and Girls in Science, we celebrate women and girls in Science, Technology, Engineering, and Mathematics (STEM) fields. One initiative for this edition focuses on women in the optical/infrared interferometric community, with participation from around the world. Community participation was sought by sending around an announcement of the initiative. Subsequent questionnaires were sent to interested participants. In this talk, I will present the results, giving visibility to the women working in the optical/infrared interferometric scientific community. I will illustrate the current participation of women in the field, and present the community insights on the current challenges and the way ahead. I will open the floor for discussion in and outside this specific scientific community, seeking similarities, differences, and perceptions on how to move forward to normalise women participation in astronomy.

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.

Reflected light observations will soon open a new frontier in the characterization of nearby rocky exoplanets. ESO facilities, starting with VLT/RISTRETTO and soon ELT/ANDES and ELT/PCS, will enable spectroscopy and possibly polarimetry of non-transiting planets such as Proxima b as spatially unresolved worlds. Reflected light encodes key atmospheric and surface properties, including potential habitability tracers like liquid water and surface heterogeneity. We observe Earth as an exoplanet using Earthshine—sunlight reflected by Earth onto the darker portion of the visible Moon—capturing our planet as a single pixel. Using 3D radiative transfer models with realistic clouds, surface albedo, and ocean reflectance, we test the detectability of signatures such as ocean glint and the primary rainbow, which probe surface liquid water and cloud microphysics. This work establishes Earthshine as a benchmark for interpreting future reflected-light observations of nearby rocky exoplanets.

Studying the chemical composition of the warm gas surrounding embedded solar-type protostars is one of the areas for which the Atacama Large Millimeter/submillimeter Array (ALMA) is particularly well suited. Since Cycle 9, the ALMA Large Program “Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)” carried out an observing campaign of a sample of 11 protostellar regions to investigate the chemical impact of their environments and evolutionary stages. This JAO talk will be a mix of technical and scientific, providing an overview of the experience of proposing, preparing, and executing the observations and subsequent data analysis for a Large Program. We recently submitted the first series of scientific papers by the COMPASS collaboration, addressing topics of spatial distribution of complex organic species and their relative abundances, variations among oxygen- and nitrogen-bearing species, methanol and its isotopic fractionation, methyl cyanide isotopologues, a class I methanol maser transition and its association with acetaldehyde. Based on our experience, I’ll summarize the benefits and challenges of unbiased spectral surveys, as well as opportunities in the era of ALMA’s Wideband Sensitivity Upgrade.

Environmental interactions in the densest regions of the cosmic web are a major driver of accelerated galaxy evolution. It is widely accepted that the cold gas reservoirs of cluster galaxies, which fuel star formation and regulate how galaxies evolve, are the components most strongly affected by environmental processes. Ram pressure stripping is one of the most prominent mechanisms driving galaxy evolution in clusters and is often manifested by asymmetric, tailed atomic gas disks. Recent MeerKAT H I observations revealed that this process is acting on a population of starburst galaxies in the Hydra I cluster (de la Casa et al. 2025). This raises the question: is RPS removing gas while simultaneously accelerating its conversion into stars, thus increasing even more the quenching rate of cluster galaxies?

In this talk, I will present a detailed study of the cold gas content of four extremely ram pressure stripped galaxies in the core of the Hydra I cluster that nonetheless exhibit relatively high star formation rates. I will show how their molecular gas distributions, traced by CO(1–0) emission observed with ALMA, as well as the molecular-to-atomic gas fractions, reveal an evolutionary path shaped by RPS. Finally, I will discuss how the stage of ram pressure stripping can be linked to a galaxy’s orbital history and how it can be traced in projected phase space.

Japanese-South American Supernovae (J-SAS) 2026 three-day mini workshop.

The chemical composition of ionized gas is a key tracer of galaxy evolution, but measuring it presents significant challenges. In this lecture, I will introduce the principal tracers of chemical abundances in ionized gas, discuss the main methods used to estimate them, and outline their advantages and limitations. Finally, I will highlight the main sources of uncertainty in abundance measurements and their impact on our understanding of galactic evolution.

A thousand hours of XMM observation time have been allocated to the FornaX Heritage project, making it the largest program since the launch of XMM.

Observations of the Euclid Fornax deep field began in 2024 and will be completed in 2027. The program will achieve unrivalled sensitivity over 10 square degrees in the X-ray, optical, and infrared domains, making the dataset and expected scientific results unique. A few hundred clusters as well as a few thousand AGN will be detected. Around 50 scientists are participating in the project.

During this seminar, we will discuss the scientific motivations of the FornaX project as well as the many challenges related to data reduction and scientific analysis. We will describe the work organization within the collaboration, its implementation in the Euclid consortium structure, and the possibility of involving external scientists.

Numerous follow-up programs will be undertaken to enhance the XMM catalogue of clusters and AGNs (spectroscopic campaigns, detailed studies of particular objects, etc.). Ideas and contributions of ESO scientists will be greatly appreciated!

Website of the FornaX project: https://fornax.cosmostat.org/

This talk will present an overview of the Yebes Radio Astronomy Observatory, located in the municipality of Yebes (Guadalajara, Spain). Its main facilities will be described, along with a review of the most relevant technical and scientific developments carried out at the observatory. In addition, a summary of the results obtained from radio frequency interference (RFI) measurements performed at the OSF and AOS in the 72–90 GHz frequency range during a research stay at the ALMA Observatory will be presented.

The Magnetic activity of cool stars is connected to the stellar age. The activity-rotation relations combined with Gyrochronology give us the big picture of the evolution of cool star activity. However, how similar could co-eval Gyr old stars of the same metallicity and similar mass be in terms of magnetic activity? Little is understood about this intrinsic scatter of activity in cool stars. It is, however, an essential piece of information required to understand the variability in the stellar environment over giga-years of stellar evolution. Including having implications on the evapouration of exoplanetary atmospheres. In my talk, We investigate this scatter using a statistically relevant sample of wide binaries. I show how the co-eval nature of wide binaries can be exploited to find this intrinsic scatter in the activity of cool stars. I additionally present how future works could use this scatter to constrain the activity-age relationship of Gyr old cool stars.

I will present recent ALMA molecular-line studies of nearby star-forming galaxies from the PHANGS survey, with a focus on the dense molecular gas that is most closely linked to active star formation. I will begin with a brief overview of the PHANGS project, which aims to understand the baryon life cycle in galaxies on the scales of individual molecular clouds by combining observations across the electromagnetic spectrum from state-of-the-art facilities such as HST, JWST, VLT, and ALMA. I will then highlight my work within the PHANGS collaboration that extends beyond the low–critical density CO lines observed by the PHANGS–ALMA survey (Leroy et al. 2021). In particular, the ACA Large-sample Mapping of Nearby galaxies in Dense gas (ALMOND) survey (Neumann et al. 2023a, 2025) targets dense molecular gas traced by high–critical density transitions such as HCN(1–0), HCO⁺(1–0), and CS(2–1), which are more directly connected to the local star formation rate in galaxies. Together with additional ALMA pilot studies (Neumann et al. 2024, and work in preparation), these observations demonstrate ALMA’s unique capability to map dense gas tracers across the nearby galaxy population. These data provide new insights into key questions of galaxy evolution and star formation: Is there a universal star formation law? How efficiently is dense molecular gas converted into stars? How do the physical conditions of the gas regulate star formation, and how are these processes influenced by galactic environment and external conditions?

Galaxy clusters constitute a key cosmological probe as their properties are sensitive both to the geometry of the universe and to the growth of cosmic structures. We will review the various cosmological tests involving clusters. We shall then focus on the cosmological forward-modelling of the X-ray properties of the cluster population, which allows bypassing the direct computation of individual cluster masses. Finally, we shall present recent developments using artificial intelligence, allowing for cosmological simulation-based inference; the method relies on purely observable (cosmology-independent) quantities and avoids any use of (cosmology-dependent) mass-observable relations.

The James Webb Space Telescope (JWST) is the most complex and sensitive space observatory ever deployed, combining revolutionary engineering with unprecedented scientific capability. With its segmented 6.5-meter primary mirror and suite of infrared instruments, JWST enables observations of the Universe with extraordinary sensitivity and angular resolution. In this talk, I will discuss the key technical innovations that underpin JWST’s performance, as well as the challenges and excitement of on-orbit commissioning. I will also address some of the operational and technical obstacles encountered during the first years of science operations. Finally, I will highlight a selection of scientific results and demonstrate how JWST’s engineering design directly enables these new discoveries.

Clusters are the largest gravitationally bound entities in the universe and are located at the nodes of the cosmic web. Paradoxically, in these objects, whose mass ranges between 1E13 and 1E16 Mo, the mass of galaxies is negligible. But the interactions between intra-cluster gas and galaxies make clusters very interesting physics laboratories. We will discuss the different methods used to detect galaxy clusters across the electromagnetic spectrum, focusing on the role of the X-ray band in both detection and physics of their evolution.

We will also review the current challenges associated with numerical simulations of clusters.