Abstract:
Rich groups and clusters of galaxies are immersed in hot X-ray emitting gas. In the absence of reheating, the X-ray gas around the cluster core should cool rapidly and flow towards the cluster center in a phenomenon known as an X-ray cooling flow. Although predicted about 30 years ago, subsequent searches for the resultant cool gas or its products (stars) have failed to find material at quantities anywhere near the predicted levels. Observations this decade show that the X-ray gas around the cluster center is strongly reheated by the AGN in the central (dominant) galaxy, which can strongly mitigate if not quench the cooling flow.
Although not at the quantities originally predicted, many central galaxies in putative cooling-flow clusters are known to contain large amounts of relatively cool gas, the dominant component of which is in the form of cool molecular gas traced in CO. Does this cool gas trace a cooling flow, or is it acquired through mergers with gas-rich galaxies? Here, I report our observations of CO in Perseus A, the central dominant galaxy in the Perseus Cluster, the X-ray-brightest cluster in the sky. I show that the behavior and properties of this gas are consistent with the predictions of an X-ray cooling flow, thus providing the most direct evidence yet for such a flow in any cluster. I describe the relationship between the cool molecular gas and other gas components at higher temperatures, and examine the possible fate of this gas.
Coffee and tea will be served 20 minutes prior to the seminar.