Seminars and Colloquia at ESO Santiago

May 2026

26/05/26 (Tuesday)

15:30, Library (ESO, Vitacura) | ESO Santiago

TMT (30 minutes talk)

Talk — Detecting Exoplanets around Early-Type Stars: Overcoming Observational Biases

Marek Skarka (Astronomical Institute of the Czech Academy of Sciences)

View Abstract

Abstract

The scarcity of known exoplanets around stars earlier than spectral type

F5 represents a major gap in current exoplanet demographics. This

apparent lack is most likely caused by strong observational biases

rather than an intrinsic absence of planetary systems. Consequently, the

occurrence rates and properties of planets around early-type stars

remain poorly constrained, limiting our understanding of planet

formation in this mass regime. Both major detection techniques face

significant challenges in this domain. The transit method is less

efficient due to the large radii of early-type stars, which reduce

transit depths, while the radial velocity method is hindered by the

scarcity of spectral lines and their rotational broadening. In this

talk, I will discuss strategies to mitigate these limitations, with a

particular focus on metallic chemically peculiar (Am) stars, which

provide more favourable conditions for radial velocity measurements. I

will also present the current performance of the PLATOSpec instrument at

La Silla Observatory and demonstrate its capabilities for detecting

exoplanets.

June 2026

01/06/26 (Monday)

15:30, Library (ESO, Vitacura) | ESO Santiago

TMT (30 minutes talk)

Talk — Hot Gas, Cold Gas, and Stars: Mapping the Halo Baryon Budget in the Local Universe

Ajay Dev (International Centre for Radio Astronomy Research, Perth, Australia)

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Abstract

Understanding how galaxies acquire, retain, and lose their baryons is a central problem in galaxy formation. Feedback processes, particularly from active galactic nuclei (AGN), are thought to redistribute baryons within dark matter haloes, displacing gas to large radii or ejecting it entirely. This leads to baryon fractions significantly below the cosmic mean, especially in low-mass systems where feedback energy can rival the halo binding energy. While hydrodynamic simulations predict strong mass-dependent baryon loss, observational constraints remain limited, particularly at group scales.

In this talk, I will present results from my PhD work, which provide a systematic, multi-wavelength empirical analysis of the baryon content of haloes in the local Universe across a wide halo mass range (1e10 – 1e15 Msol). Combining radio (ASKAP, ALFALFA), optical (GAMA, 4MOST/WAVES), and X-ray (eROSITA) datasets, I measure the contributions of cold gas, stars, and hot gas to the total halo baryon budget.

Using these measurements, I construct baryon mass–halo mass relations and combine them with halo mass functions to derive the distribution of baryons across cosmic structures. These results provide new observational constraints on baryon retention and depletion as a function of halo mass, highlighting a significant baryon deficit in group-scale systems. I will conclude by discussing the implications of these results for feedback processes and galaxy evolution, and outline how upcoming surveys will enable these measurements to be extended across cosmic time.

03/06/26 (Wednesday)

14:30, Library (ESO, Vitacura) | ESO Santiago

Python Coffee

Talk — iSpec Tool

Ivanna Hernandez (ESO)

View Abstract

Abstract

iSpec is a tool designed for the treatment and analysis of stellar spectra. It facilitates a wide range of spectroscopic tasks, including continuum normalization, resolution degradation, radial velocity correction, atmospheric parameter determination, and chemical abundance analysis.

In addition, iSpec enables the determination of stellar atmospheric parameters for F, G, K, and M-type stars. These parameters can be derived using two complementary approaches: the synthetic spectral-fitting technique and the equivalent-width method.

The software integrates MARCS and ATLAS model atmospheres and supports several widely used radiative transfer codes, including SPECTRUM, Turbospectrum, SME, MOOG, and Synthe/WIDTH9.

In this Python Coffee, I will give a practical introduction to iSpec using a solar spectrum as an example. I will show how to use its graphical interface to perform basic steps such as continuum normalization, radial velocity correction, stellar parameter estimation, and chemical abundance determination. The goal is to provide a first overview of the tool and its main capabilities for stellar spectroscopy .

04/06/26 (Thursday)

15:30, Library (ESO, Vitacura) | ESO Santiago

TMT (30 minutes talk)

Talk — Tracing the Invisible: The Shape of Cluster Haloes revealed by the Intracluster Light

Tutku Kolcu (University of Nottingham)

View Abstract

Abstract

The intracluster light (ICL) offers a uniquely luminous probe of galaxy cluster halo shape and orientation, but its extremely low surface brightness has historically made robust cluster-scale morphological measurements challenging. In this talk, I will present ICL ellipticity and position-angle measurements from Euclid’s Quick Release (Q1) for nearly 200 clusters at 0.1 ≤ z ≤ 0.8, selected from the eROSITA All-Sky Survey and the Dark Energy Survey. We quantify ICL morphology across five bands (VIS, Y, J, H, and coadded YJH), finding consistent shape parameters across filters, with the H band tracing the ICL to the largest cluster-centric radii. The ellipticity distribution peaks at e ≃ 0.5, in close agreement with halo ellipticities from strong and weak lensing, supporting the view that the ICL traces the cluster's large-scale structure. Radially, BCG-dominated cores are relatively round (e ≃ 0.2), while the diffuse component becomes progressively more elongated, reaching e ≃ 0.5 by 0.1R₂₀₀ (~100 kpc). By stacking clusters in redshift bins, we extend surface-brightness constraints to ~0.8 R₂₀₀ and ellipticity measurements to ~0.4R₂₀₀ (350–400 kpc), where we observe an ellipticity plateau beyond ~0.1R₂₀₀ with no detectable redshift evolution, challenging theoretical expectations.

To bridge observations and theory, we compare to Hydrangea simulations using two complementary ICL definitions: (i) a theoretical “unbound” ICL+BCG component, and (ii) fully forward-modelled mock observations that include subhaloes and realistic backgrounds. The unbound ICL is systematically rounder, while the forward-modelled distribution matches the observed distribution well—highlighting that forward-modelling is essential for direct comparisons when observational processing and measurement extraction are imperfect. Overall, our methodology provides a benchmark for testing hydrodynamical simulations and forthcoming Euclid data releases will enable substantially tighter statistical constraints.

11/06/26 (Thursday)

15:30, Library (ESO, Vitacura) | ESO Santiago

TMT (30 minutes talk)

Talk — to be announced

Hanna Kasperer (Universidade do Porto)

View Abstract