Within the Directorate for Science at its Headquarters in Garching, near Munich, Germany, ESO is inviting university students to apply to our ESO Summer Research Programme. The ESO Summer Research Programme is an opportunity for university students from science, technology, engineering, and mathematics (STEM) fields who have not yet started a PhD programme and have completed at least two years of their degree.

Within the scope of this programme, there are seven exciting individual projects topics to choose from. Please visit https://eso.org/sci/meetings/2026/SummerResearch2026.html to review all seven project topics, as you can only apply to one.

Applications for the ESO Summer Research Programme will be considered from students taking any astronomy, physical science, computer science or mathematical degree subjects. However, it is expected that students have some knowledge of physics, programming, data analysis techniques and, preferably, astronomy.

Students will be selected for the programme based on their academic achievements, research potential and likelihood to significantly benefit from the experience. Particular attention will be given to the motivation of the students to join the programme and specific motivation for Project A:

Project A: Assessing Assembly Bias Through the Satellite Populations of X-ray–Selected Halos

Supervisors: Ilaria Marini, Victoria Toptun, Natanael de Isidio

Galaxy groups and clusters are key environments for studying how galaxies evolve, because satellite galaxies in these systems experience a range of physical processes - such as gas stripping, starvation, and tidal interactions - that depend strongly on their surroundings. A useful way to characterize these environments is through their X-ray luminosity (Lx), which reflects the amount and density of hot gas in the system. Since Lx is linked not only to halo mass but also to a system's formation history and the density of the surrounding large-scale structure, it may serve as a broader indicator of environmental conditions and possible assembly bias.

This project will investigate how the properties of satellite galaxies - such as colors, star-formation activity, stellar masses, and simple morphology indicators - vary across groups and clusters with different X-ray luminosities. By combining X-ray-selected systems with optical galaxy data, and by using either observational datasets and/or cosmological simulations, the study will test whether Lx provides information about galaxy evolution that goes beyond what halo mass alone can account for.