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Cold molecular gas in cooling flow clusters

Philippe Salome, IRAM

Central cluster galaxies are very interesting to study the mechanisms that lead the formation and evolution of galaxies through gas accretion. Recent progress in X-ray (past decade) have considerably changed the understanding of central cluster physics. We focus on the millimeter window to search for cold gas (10-100 K) and found CO emission lines around many brightest cluster galaxies. We then made the first maps of the cold gas emission, showing the important role of the AGN hosted by the central galaxy. More recently, we found extented emission, for the first time resolved into filaments of very cold gas around NGC~1275. The AGN appears to regulate the amount of gas cooling and forming stars. These results open exciting questions for the next generation of infrared and millimeter sub-millimeter facilities like ALMA and HERSCHEL.