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Cold gas dynamics in Hydra-A : evidence for a rotating disc.

Hamer, S.L. and Edge, A.C. and Swinbank, A.M. and Oonk, J.B.R. and Mittal, R. and McNamara, B.R. and Russell, H.R. and Bremer, M.N. and Combes, F. and Fabian, A.C. and Nesvadba, N.P.H. and O'Dea, C.P. and Baum, S.A. and Salomé, P. and Tremblay, G. and Donahue, M. and Ferland, G.J. and Sarazin, C.L. (2014) 'Cold gas dynamics in Hydra-A : evidence for a rotating disc.', Monthly notices of the Royal Astronomical Society., 437 (1). pp. 862-878.


We present multifrequency observations of the radio galaxy Hydra-A (3C218) located in the core of a massive, X-ray luminous galaxy cluster. Integral field unit spectroscopy is used to trace the kinematics of the ionized and warm molecular hydrogen which are consistent with an ∼5 kpc rotating disc. Broad, double-peaked lines of CO(2–1), [C II] 157 μm and [O I] 63 μm are detected. We estimate the mass of the cold gas within the disc to be Mgas = 2.3 ± 0.3 × 109 M⊙. These observations demonstrate that the complex line profiles found in the cold atomic and molecular gas are related to the rotating disc or ring of gas. Finally, a Hubble Space Telescope image of the galaxy shows that this gas disc contains a substantial mass of dust. The large gas mass, star formation rate and kinematics are consistent with the levels of gas cooling from the intracluster medium (ICM). We conclude that the cold gas originates from the continual quiescent accumulation of cooled ICM gas. The rotation is in a plane perpendicular to the projected orientation of the radio jets and ICM cavities hinting at a possible connection between the kpc-scale cooling gas and the accretion of material on to the black hole. We discuss the implications of these observations for models of cold accretion, AGN feedback and cooling flows.

Item Type:Article
Keywords:Galaxies: clusters: individual: Hydra-A, Galaxies: clusters: intracluster medium, Galaxies: elliptical and lenticular, cD
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2014 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:19 June 2014
Date of first online publication:January 2014
Date first made open access:No date available

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