Abstract

Invited Talk - Plenary

Wednesday, 09 September 2026, 09:00   (MW-1801 / virtual plenum)

Cosmology and Baryons Across Scales: Probing Halo Mass Function to Cosmic Filaments with eROSITA

Esra Bulbul
MPE, Garching

While baryons are expected to trace the underlying dark matter, their thermodynamic evolution is governed by the complex interplay between gravitational collapse and feedback from the central black hole. This feedback redistributes a large fraction of baryons into diffuse gas across the cosmic web, from galaxy groups to filaments, shaping the observables we use for precision cosmology. The eROSITA instrument on board the Spectrum-RG mission provides the unprecedented statistical power required to map these structures and conduct a simultaneous census of baryon physics and the large-scale structure of the Universe. I will present results on the distribution and physical state of baryons across scales by combining eROSITA X-ray data with multi-wavelength data. Central to this work is the eROSITA galaxy group and cluster sample, which provides competitive constraints on cosmological parameters by measuring the halo mass function and its redshift evolution, with support from optical surveys such as DESI, DES, HSC, and KiDS. I will further discuss how probing the diffuse, warm-hot plasma in galaxy groups, clusters, and cosmic filaments allows us to study feedback. Together, these measurements link small-scale astrophysics with global cosmology, improving our understanding of the baryon budget and the fundamental parameters governing structure formation.