Chandra Observat ions of Clusters of Galaxies

We discuss two themes from Chandra cluster observations. First, we describe the interaction of buoyant, radio emitting plasma bubbles with the hot intracluster gas. Second we summarize the Chandra observations of "cold" fronts (sharp discontinuities in gas density and temperature) separating cool, denser gas clouds from the hotter intracluster medium. 1. The Radio — X-ray Interaction or Bubbles, Bubbles Everywhere Prior to the launch of Chandra, ROSAT observations of NGC1275 and M87 provided hints of complex interactions between radio emitting plasmas ejected from central galaxies in clusters (e.g., Bohringer et al. 1993, 1995; Churazov et al. 2000a). The prevalence of the interaction between the radio emitting plasma and the hot intracluster medium (ICM) has increased dramatically with the launch of Chandra. In the Hydra A cluster, Chandra observations showed cavities created by the inner radio lobes as they displaced the X-ray gas (McNamara et al. 2000). In addition, a complex X-ray enhancement is associated with the northern buoyant radio bubble (Taylor et al. 1990). For NGC1275/Perseus, Fabian et al. (2000) showed that the bright edges around the X-ray holes (radio lobes) were not produced by shocks since their emission was softer than that of the ambient hot gas. Finoguenov & Jones (2000) found a very complex structure for the X-ray emitting gas around the Virgo galaxy M84 (NGC4374) that is determined by the morphology of the radio lobes. The ACIS Centaurus A image shows an X-ray enhancement just in advance of the leading edge of the southern inner radio lobe (see Kraft et al. 2000 for a discussion of the HRC image). In a study of M87, Churazov et al. (2000b) combined the new radio image of Owen, Eilek, & Kassim (2000) with the ROSAT HRI data to describe the interaction of buoyant bubbles with the X-ray emitting hot gas and to explain many features seen in clusters and around galaxies as the radio plasma interacts with the hot gas. They liken the behavior of the bubbles to that of atmospheric