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Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795

Russell, H.R.; McNamara, B.R.; Fabian, A.C.; Nulsen, P.E.J.; Combes, F.; Edge, A.C.; Hogan, M.T.; McDonald, M.; Salomé, P.; Tremblay, G.; Vantyghem, A.N.

Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795 Thumbnail


H.R. Russell

B.R. McNamara

A.C. Fabian

P.E.J. Nulsen

F. Combes

M.T. Hogan

M. McDonald

P. Salomé

G. Tremblay

A.N. Vantyghem


We present new ALMA observations tracing the morphology and velocity structure of the molecular gas in the central galaxy of the cluster Abell 1795. The molecular gas lies in two filaments that extend 5–7 kpc to the N and S from the nucleus and project exclusively around the outer edges of two inner radio bubbles. Radio jets launched by the central active galactic nucleus have inflated bubbles filled with relativistic plasma into the hot atmosphere surrounding the central galaxy. The N filament has a smoothly increasing velocity gradient along its length from the central galaxy’s systemic velocity at the nucleus to −370kms−1 −370kms−1 , the average velocity of the surrounding galaxies, at the furthest extent. The S filament has a similarly smooth but shallower velocity gradient and appears to have partially collapsed in a burst of star formation. The close spatial association with the radio lobes, together with the ordered velocity gradients and narrow velocity dispersions, shows that the molecular filaments are gas flows entrained by the expanding radio bubbles. Assuming a Galactic XCO factor, the total molecular gas mass is 3.2 ± 0.2 × 109 M⊙. More than half lies above the N radio bubble. Lifting the molecular clouds appears to require an infeasibly efficient coupling between the molecular gas and the radio bubble. The energy required also exceeds the mechanical power of the N radio bubble by a factor of 2. Stimulated feedback, where the radio bubbles lift low-entropy X-ray gas that becomes thermally unstable and rapidly cools in situ, provides a plausible model. Multiple generations of radio bubbles are required to lift this substantial gas mass. The close morphological association then indicates that the cold gas either moulds the newly expanding bubbles or is itself pushed aside and shaped as they inflate.


Russell, H., McNamara, B., Fabian, A., Nulsen, P., Combes, F., Edge, A., …Vantyghem, A. (2017). Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795. Monthly Notices of the Royal Astronomical Society, 472(4), 4024-4037.

Journal Article Type Article
Acceptance Date Sep 7, 2017
Online Publication Date Sep 7, 2017
Publication Date Dec 21, 2017
Deposit Date Oct 20, 2017
Publicly Available Date Oct 20, 2017
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 472
Issue 4
Pages 4024-4037


Published Journal Article (3.2 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017. The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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