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It is widely believed that structure in the Universe evolves hierarchically, as primordial density fluctuations, amplified by gravity, collapse and merge to form progressively larger systems. The structure and evolution of X-ray clusters, however, seems at odds with this hierarchical scenario for structure formation. Poor clusters and groups, as well as most distant clusters detected to date, are substantially fainter than expected from the tight relations between luminosity, temperature and redshift predicted by these models. Here we show that these discrepancies arise because, near the centre, the entropy of the hot, diffuse intracluster medium (ICM) is higher tha$ achievable through gravitational collapse, indicating substantial non-gravitational heating of the ICM. We estimate this excess entropy for the first time, and argue that it represents a relic of the energetic winds through which forming galaxies polluted the ICM with metals. Energetically, this is onl$ possible if the ICM is heated at modest redshift ($z ltsim 2$) but prior to cluster collapse, indicating that the formation of galaxies precedes that of clusters and that most clusters have been assembled very recently.
We present a new model for the X-ray properties of the intracluster medium that explicitly includes heating of the gas by the energy released during the evolution of cluster galaxies. We calculate the evolution of clusters by combining the semi-analy
The majority of baryons reside beyond the optical extent of a galaxy in the circumgalactic and intergalactic media (CGM/IGM). Gaseous halos are inextricably linked to the appearance of their host galaxies through a complex story of accretion, feedbac
X-ray spectra of galaxy clusters are dominated by the thermal emission from the hot intracluster medium. In some cases, besides the thermal component, spectral models require additional components associated, e.g., with resonant scattering and charge
We present the first three galaxy clusters of a larger sample of the most X-ray luminous galaxy clusters selected from the ROSAT Bright Survey. This project, which is a systematic search for strong lensing, aims at arc statistics, mass determinations
We investigate the role of radiative cooling within the core of large X-ray clusters using multi-phase hydrodynamics. We developed for that purpose a spherically symmetric hydrodynamical code, coupled to a fluid model that describes accurately the da