The Impact of Galaxy Formation on the X-ray Evolution of Clusters

Preprint
Publisher Website
Google Scholar
Abstract
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 formation of cluster galaxies. We calculate the evolution of clusters by combining the semi-analytic model of galaxy formation of Cole et al. with a simple model for the thermodynamic properties of the intracluster medium. We focus on the cluster X-ray luminosity function and on the relation between X-ray temperature and luminosity (the T-L relation). These properties are known to disagree with predictions of simpler cluster models based on scaling relations which neglect gas cooling and heating processes. We show that cooling alone is not enough to account for the flatness of the observed T-L relation or for the lack of strong redshift evolution in the observed X-ray luminosity function. Gas heating, on the other hand, can solve these two problems: in the Lambda-CDM cosmology, our model reproduces fairly well the T-L relation and the X-ray luminosity function and, furthermore, predicts only weak evolution in these two properties out to z=0.5, in agreement with recent observational data. A successful model requires an energy input of 1--2 h^{-1/2} 10^49 ergs per solar mass of stars formed. This is comparable to the total energy released by the supernovae associated with the formation of the cluster galaxies. Our model therefore requires a (perhaps unrealistically) high efficiency for the absorption of supernovae energy by the intracluster gas, or additional sources of energy, such as mechanical energy from AGN winds. The amplification of an initial energy input by the response of the intracluster medium to protocluster mergers might ease the energy requirements.

This publication has 0 references indexed in Scilit: