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A molecular absorption line survey toward the AGN of Hydra-A.

Peck, A.B. and Oonk, J.B.R. and O’Dea, C. and Nesvadba, N. and Ferland, G. and Fabian, A.C. and Donahue, M. and Bremer, M.N. and Baum, S.A. and Tremblay, G.R. and Sarazin, C. and Salomé, P. and Gaspari, M. and Russell, H. and McNamara, B.R. and Hamer, S. and Combes, F. and Edge, A.C. and Rose, T. (2020) 'A molecular absorption line survey toward the AGN of Hydra-A.', Monthly notices of the Royal Astronomical Society., 496 (1). pp. 364-380.


We present Atacama Large Millimeter/submillimeter Array observations of the brightest cluster galaxy Hydra-A, a nearby (z = 0.054) giant elliptical galaxy with powerful and extended radio jets. The observations reveal CO(1-0), CO(2-1), 13CO(2-1), CN(2-1), SiO(5-4), HCO+(1-0), HCO+(2-1), HCN(1-0), HCN(2-1), HNC(1-0) and H2CO(3-2) absorption lines against the galaxy’s bright and compact active galactic nucleus. These absorption features are due to at least 12 individual molecular clouds which lie close to the centre of the galaxy and have velocities of approximately −50 to +10 km s−1 relative to its recession velocity, where positive values correspond to inward motion. The absorption profiles are evidence of a clumpy interstellar medium within brightest cluster galaxies composed of clouds with similar column densities, velocity dispersions and excitation temperatures to those found at radii of several kpc in the Milky Way. We also show potential variation in a ∼10 km s−1 wide section of the absorption profile over a two year timescale, most likely caused by relativistic motions in the hot spots of the continuum source which change the background illumination of the absorbing clouds.

Item Type:Article
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2020 The Author(s) . Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:16 May 2020
Date deposited:29 May 2020
Date of first online publication:28 May 2020
Date first made open access:18 June 2020

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