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The X-ray Ribs Within the Cocoon Shock of Cygnus A

Duffy, R.T.; Worrall, D.M.; Birkinshaw, M.; Nulsen, P.E.J.; Wise, M.W.; de Vries, M.N.; Snios, B.; Mathews, W.G.; Perley, R.A.; Hardcastle, M.J.; Rafferty, D.A.; McNamara, B.R.; Edge, A.C.; McKean, J.P.; Carilli, C.L.; Croston, J.H.; Godfrey, L.E.H.; Laing, R.A.

The X-ray Ribs Within the Cocoon Shock of Cygnus A Thumbnail


R.T. Duffy

D.M. Worrall

M. Birkinshaw

P.E.J. Nulsen

M.W. Wise

M.N. de Vries

B. Snios

W.G. Mathews

R.A. Perley

M.J. Hardcastle

D.A. Rafferty

B.R. McNamara

J.P. McKean

C.L. Carilli

J.H. Croston

L.E.H. Godfrey

R.A. Laing


We use new and archival Chandra observations of Cygnus A, totalling ∼1.9 Ms, to investigate the distribution and temperature structure of gas lying within the projected extent of the cocoon shock and exhibiting a rib-like structure. We confirm that the X-rays are dominated by thermal emission with an average temperature of around 4 keV, and have discovered an asymmetry in the temperature gradient, with the southwestern part of the gas cooler than the rest by up to 2 keV. Pressure estimates suggest that the gas is a coherent structure of single origin located inside the cocoon, with a mass of roughly 2 × 1010M⊙. We conclude that the gas is debris resulting from disintegration of the cool core of the Cygnus A cluster after the passage of the jet during the early stages of the current epoch of activity. The 4 keV gas now lies on the central inside surface of the hotter cocoon rim. The temperature gradient could result from an offset between the centre of the cluster core and the Cygnus A host galaxy at the switch-on of current radio activity.


Duffy, R., Worrall, D., Birkinshaw, M., Nulsen, P., Wise, M., de Vries, M., …Laing, R. (2018). The X-ray Ribs Within the Cocoon Shock of Cygnus A. Monthly Notices of the Royal Astronomical Society, 476(4), 4848-4860.

Journal Article Type Article
Acceptance Date Feb 26, 2018
Online Publication Date Mar 3, 2018
Publication Date May 1, 2018
Deposit Date Mar 29, 2018
Publicly Available Date Mar 29, 2018
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 476
Issue 4
Pages 4848-4860
Related Public URLs


Accepted Journal Article (1.3 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society] ©: 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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