Radially inflowing molecular gas in NGC 1275 deposited by an x-ray cooling flow in the perseus cluster

Abstract

We have imaged in CO(2-1) the molecular gas in NGC 1275 (Perseus A), the cD galaxy at the center of the Perseus Cluster, at a spatial resolution of ∼1 kpc over a central region of radius ∼10 kpc. Per A is known to contain ∼1.3 × 10 10 M ⊙ of molecular gas, which has been proposed to be captured from mergers with or ram pressure stripping of gas-rich galaxies, or accreted from a X-ray cooling flow. The molecular gas detected in our image has a total mass of ∼4 × 10 9 M ⊙, and for the first time can be seen to be concentrated in three radial filaments with lengths ranging from at least 1.1 to 2.4 kpc, all lying in the east-west directions spanning the center of the galaxy to radii of ∼8 kpc. The eastern and outer western filaments exhibit larger blueshifted velocities with decreasing radii, whereas the inner western filament spans the systemic velocity of the galaxy. The molecular gas shows no signature of orbital motion, and is therefore unlikely to have been captured from gas-rich galaxies. Instead, we are able to reproduce the observed kinematics of the two outer filaments as free fall in the gravitational potential of Per A, as would be expected if they originate from a X-ray cooling flow. Indeed, all three filaments lie between two prominent X-ray cavities carved out by radio jets from Per A, and closely resemble the spatial distribution of the coolest X-ray gas in the cluster core. The inferred mass deposition rate into the two outermost filaments alone is roughly 75 M ⊙ yr -1. This cooling flow can provide a nearly continuous supply of molecular gas to fuel the active nucleus in Per A. © 2008. The American Astronomical Society. All rights reserved.