Institute for Advanced Study/Princeton University Joint Astrophysics Colloquium

During its brief period of operation, the Hitomi X-ray observatory (known as Astro-H prior to launch) has observed the Perseus galaxy cluster as a first-light target. This has been a long-awaited first look at a galaxy cluster with an X-ray calorimeter, which provided a qualitative leap in energy resolution (by factor 20-30) for extended celestial sources. Such resolution is sufficient to detect Doppler shifts and broadening of atomic lines caused by motions and turbulence in the intracluster plasma. The core of the Perseus cluster is a site where all the physical processes that govern cluster evolution combine -- runaway radiative cooling, AGN heating, large-scale sloshing of the core gas, acceleration of ultrarelativistic electrons, and interaction between the plasma and the cold molecular gas. The Hitomi spectrum is a treasure trove of emission lines from various ions that contain dynamical as well as chemical information. Our analysis reveals a rather quiescent velocity field for such a visibly disturbed object. We also did not detect the 3.5 keV emission line, considered a possible signal from the dark matter decay, at the flux previously reported by XMM (an instrument with a much lower energy resolution). I will present these and other preliminary results from the ongoing analysis of the first-ever high-resolution cluster spectrum.