A High‐Resolution Study of the Hydra A Cluster withChandra: Comparison of the Core Mass Distribution with Theoretical Predictions and Evidence for Feedback in the Cooling Flow

The cooling flow cluster Hydra A was observed during the orbital activationand calibration phase of the Chandra Observatory. While the X-ray image of thecluster exhibits complex structure in the central region as reported inMcNamara $etal$, the large scale X-ray morphology of the cluster is fairlysmooth. A spectroscopic analysis of the ACIS data shows that the gastemperature in Hydra A increases outward, reaches a maximum temperature of 4keV at 200 kpc, and then decreases slightly at larger radii. The distributionof heavy elements is nonuniform, with a factor of two increase in the Fe and Siabundances within the central 100 kpc. Beyond the central 100 kpc the Si-to-Feabundance ratio is twice solar, while the Si-to-Fe ratio of the central excessis consistent with the solar value. One of the more surprising results is thelack of spectroscopic evidence for multiphase gas within the bulk of thecooling flow. Beyond the central 30 kpc, the ACIS spectra are adequately fitwith a single temperature model. The addition of a cooling flow component doesnot significantly improve the fit. Only within the central 30 kpc (where thecooling time is less than 1~Gyr), is there spectroscopic evidence formultiphase gas. However, the spectroscopic mass deposition rate is more than afactor of 10 less than the morphologically derived mass accretion rate at 30kpc. We propose that the cooling flow region is convectively unstable due toheating by the central radio source which significantly reduces the netaccretion rate.Comment: 19 figures include