Cold molecular gas along the cooling X-ray filament in A1795

Abstract

We present the results of interferometric observations of the cool core of A1795 at CO(1-0) using the Combined Array for Research in Millimeter-wave Astronomy. In agreement with previous work, we detect a significant amount of cold molecular gas (3.9 ± 0.4 × 109 M ⊙) in the central 10kpc. We report the discovery of a substantial clump of cold molecular gas at clustercentric radius of 30kpc (2.9 ± 0.4 × 109 M ⊙), coincident in both position and velocity with the warm, ionized filaments. We also place an upper limit on the H 2 mass at the outer edge of the star-forming filament, corresponding to a distance of 60kpc (<0.9 × 109 M ⊙). We measure a strong gradient in the Hα/H2 ratio as a function of radius, suggesting different ionization mechanisms in the nucleus and filaments of A1795. The total mass of cold molecular gas (∼7 × 109 M ⊙) is roughly 30% of the classical cooling estimate at the same position, assuming a cooling time of ∼109 yr. Combining the cold molecular gas mass with the UV-derived star formation rate and the warm, ionized gas mass, the spectroscopically derived X-ray cooling rate is fully accounted for and in good agreement with the cooling byproducts over timescales of 10 9 yr. The overall agreement between the cooling rate of the hot intracluster medium and the mass of the cool gas reservoir suggests that, at least in this system, the cooling flow problem stems from a lack of observable cooling in the more diffuse regions at large radii. © © 2012. The American Astronomical Society. All rights reserved.