Seminars and Colloquia at ESO Santiago

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.