H II and H2 in the envelopes of cooling flow central galaxies

Abstract

We report observations of ionized and warm molecular gas in the extended regions of the central galaxies in several cooling flow clusters. These show that both gas phases are present in these clusters to large radii. We trace both Paα and H2 lines to radii in excess of 20 kpc. The surface brightness profiles of the two phases trace each other closely. Apart from very close to the central active galactic nucleus (AGN), line ratios in and between the phases vary only slowly with position. The kinematics of the phases are indistinguishable, and away from the influence of the central AGN both the mean and dispersion in velocity are low (≤100 km s-1), ruling out kinematic support of the molecular gas. All of the above indicate that the mechanisms for heating the molecular gas and ionizing the H II regions are highly coupled. The highest surface brightness emission within a few kiloparsecs of the central AGN is distinct, both kinematically and thermally, from that at larger radii. The relative strengths of the Paα to the H 2 lines indicate a source of ultraviolet excitation rich in extreme-ultraviolet relative to far-ultraviolet photons, e.g. a blackbody with a temperature ≥105 K. © 2005 RAS.