Speaker: Prof. Jeremy Lim (Hong Kong University)

Time: 3:00pm, July 24

Location: Large conf. room, 3rd floor

Abstract：

Galaxy clusters are permeated by hot X-ray-emitting gas. In relaxed clusters, the X-ray gas around the cluster center is predicted to cool rapidly thereby resulting in a X-ray cooling flow. All subsequent searches, however, have found much less cool gas than predicted, even in cases where molecular gas with masses of 10^9-10^11 Msun have been detected. Today, radio jets from the AGN in the central giant elliptical galaxy are believed to reheat the surrounding X-ray gas, mitigating if not entirely quenching the X-ray cooling flow. Here, I review the properties of the cool gas in the central giant elliptical galaxy of the Perseus Cluster, the X-ray-brightest cluster in the sky. I present a detailed study of its molecular gas, revealing for the first time that this gas is concentrated in multiple radial filaments unlike that seen in any other elliptical galaxy. I show that the molecular gas appears to be radially infalling, contrary to that expected if this gas has been accreted from a merger, but as would be expected if it originates from a X-ray cooling flow. I show tentative evidence that the molecular gas may be responsible for fueling the AGN in the central elliptical galaxy, completing a feedback loop of cooling and reheating of the X-ray gas.