Contstraining the Cold Gas and Dust in Cluster Cooling Flows

Science Category: Extra Galactic: Galaxy clusters/Lensing clusters Observing Modes: Pacs Line Spectroscopy, Pacs Photometer, Spire Photomete r Hours Requested: 140.5 Abstract: A major cosmological event is the formation of first massive galaxies, which evolve to the luminous elliptical galaxies of today. Star formation in these galaxies was regulated and ultimately stifled by energetic AGN feedback processes, according to simulations. However, the nature of these processes is open to speculation because at these enormous distances, observations provide few constraints. Similar processes occur in some low redshift galaxy clusters where star formation and cold gas is detected in and around the brightest cluster galaxies. These modern-day analogs provide us with the opportunity to understand the heating, cooling, and star formation that occur on a grand scale at high redshift. In this Herschel Key Project, we will determine the location and mass of cooled gas, along with its temperature, ionization state, density and cooling rate. These new data, only possible with Herschel, are supplemented by radio, X-ray, and optical studies of the stars, hot gas, and AGN activity. To accomplish our goals, we will use PACSto measure the line strengths of [01], [Dill], [Nil], [CII] and [Sil], major coolants at low temperatures that also reflect the ionization state of the gas. The requested PACSand SPIREphotometry will determine the distribution of dust temperatures and masses, including the detection of the coolest gas clouds. These datasets will reveal the pathway from the hot ambient medium to cool gas to star formation, a process that was widespread when the universe was young.