Heating of X-ray hot gas in groups by blast waves

In order to find the conditions that determine whether X-ray hot gas in galaxy groups (intragroup gas [IGG]) is heated externally or internally, we investigate the evolution of blast waves in galaxy groups growing on a hierarchical clustering scenario. We find that the blast waves driven by quasars are confined in groups and heat the IGG internally at z less than or similar to 1. However, at z greater than or similar to 1, they expel the IGG from groups; the expelled gas may fall back into the groups later as externally heated gas. Moreover, this may explain the observed low metal abundance of IGG. For blast waves driven by strong starbursts, the shift of the fate of blast waves occurs at z similar to 3. On the other hand, although blast waves driven by weak starbursts do not expel IGG from groups, the heating efficiency decreases at z greater than or similar to 3 because of radiative cooling. It will be useful to compare these results with XMM-Newton observations.