From clusters to Milky Way-type groups: Extending X-ray scaling relations with eROSITA
Victoria Toptun (ESO)
Tuesday 21/04/2026 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
Low-mass galaxy groups are the most common environments for galaxies and serve as a key bridge between cosmological structure formation and galaxy evolution. Yet, their hot gas and baryonic content remain poorly characterized, largely due to their low surface brightness in X-rays. In this talk, I will show how spectral stacking of eROSITA data offers a powerful way to uncover the X-ray properties of galaxy groups and clusters identified through large spectroscopic surveys such as SDSS and GAMA. Using eRASS1 data, I will present stacked X-ray spectra over a wide range of halo masses, from massive clusters down to group scales comparable to the Local Group, and compare them with mock observations from Magneticum hydrodynamical simulations. This approach allows us to extend and validate key X-ray scaling relations into the low-mass regime, such as the mass-temperature relation and the stellar-to-halo mass relation for brightest central galaxies. With this approach, we also probe the impact of AGN feedback on baryon content and distribution, offering new constraints on the thermodynamics and internal structure of the intra-group medium. These results open new pathways to connecting observations and theory across the full mass spectrum of cosmic structures even for systems individually undetected in X-rays