Seminars and Colloquia at ESO Santiago

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?

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.

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.

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/

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

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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.

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.

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How are the extended and low-surface brightness halos of early-type galaxies built up, and which role does their environment play in their evolution? Studying their halos provides essential insights into their accretion history as accretion and merging events leave behind long-lasting signatures. These accretion events also release stars into the intra-group light (IGL), whose assembly is closely linked with the morphological transformation of galaxies in groups and clusters.

In the first part of my talk, I will present our work charactering the haloes and surrounding IGL of nearby massive early-type galaxies in groups and clusters with planetary nebulae as discrete kinematic tracers in synergy with deep and wide-field imaging, resolved stellar population studies, and integral-field spectroscopy. In the second part of my talk, I will address the discovery space for simultaneously studying planetary nebulae and stellar populations with integral-field spectrographs such as MUSE at the VLT and SITELLE at the CFHT. I will present our pilot papers on planetary nebulae in early- and late-type galaxies and contrast our observational results with predictions from state-of-the-art simulations of post-asymptotic giant branch stellar evolution.

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Many exoplanets have been found, but still no Earth-like planet in a one-year orbit around a solar-type star. Limitations no longer stem from observations but from the physical variability of the host star, which greatly exceeds the radial-velocity modulation by an Earth-like planet.  Current observational efforts are to find planets around our Sun, monitoring the Sun-as-a-star with extreme precision radial-velocity spectrometers.  Theoretical hydrodynamic simulations produce time-variable solar spectral atlases, where radial-velocity jittering is followed in different spectral features.  A step toward exoEarth detection will be to identify dissimilar spectral lines (strong or weak, neutral or ionized, high or low excitation, etc.) with disparate responses to stellar activity, to disentangle wavelength shifts induced by exoplanets from those originating in stellar atmospheres.

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