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

Peck, A.B.; Oonk, J.B.R.; O’Dea, C.; Nesvadba, N.; Ferland, G.; Fabian, A.C.; Donahue, M.; Bremer, M.N.; Baum, S.A.; Tremblay, G.R.; Sarazin, C.; Salomé, P.; Gaspari, M.; Russell, H.; McNamara, B.R.; Hamer, S.; Combes, F.; Edge, A.C.; Rose, T.

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


A.B. Peck

J.B.R. Oonk

C. O’Dea

N. Nesvadba

G. Ferland

A.C. Fabian

M. Donahue

M.N. Bremer

S.A. Baum

G.R. Tremblay

C. Sarazin

P. Salomé

M. Gaspari

H. Russell

B.R. McNamara

S. Hamer

F. Combes


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.


Peck, A., Oonk, J., O’Dea, C., Nesvadba, N., Ferland, G., Fabian, A., …Rose, T. (2020). A molecular absorption line survey toward the AGN of Hydra-A. Monthly Notices of the Royal Astronomical Society, 496(1), 364-380.

Journal Article Type Article
Acceptance Date May 16, 2020
Online Publication Date May 28, 2020
Publication Date 2020-07
Deposit Date May 29, 2020
Publicly Available Date Jun 18, 2020
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 496
Issue 1
Pages 364-380


Accepted Journal Article (1.5 Mb)

Copyright 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.

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