We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy.

Durham Research Online
You are in:

Deep and narrow CO absorption revealing molecular clouds in the Hydra-A brightest cluster galaxy.

Rose, T. and Edge, A.C. and Combes, F. and Gaspari, M. and Hamer, S. and Nesvadba, N. and Russell, H. and Tremblay, G.R. and Baum, S.A. and O’Dea, C. and Peck, A.B. and Sarazin, C. and Vantyghem, A. and Bremer, M. and Donahue, M. and Fabian, A.C. and Ferland, G. and McNamara, B.R. and Mittal, R. and Oonk, J.B.R. and Salomé, P and Swinbank, A.M. and Voit, M. (2019) 'Deep and narrow CO absorption revealing molecular clouds in the Hydra-A brightest cluster galaxy.', Monthly notices of the Royal Astronomical Society., 485 (1). pp. 229-238.


Active galactic nuclei play a crucial role in the accretion and ejection of gas in galaxies. Although their outflows are well studied, finding direct evidence of accretion has proved very difficult and has so far been done for very few sources. A promising way to study the significance of cold accretion is by observing the absorption of an active galactic nucleus’s extremely bright radio emission by the cold gas lying along the line-of-sight. As such, we present ALMA CO(1-0) and CO(2-1) observations of the Hydra-A brightest cluster galaxy (z=0.054) which reveal the existence of cold, molecular gas clouds along the line-of-sight to the galaxy’s extremely bright and compact mm-continuum source. They have apparent motions relative to the central supermassive black hole of between -43 and -4 km s−1 and are most likely moving along stable, low ellipticity orbits. The identified clouds form part of a ∼109 M⊙, approximately edge-on disc of cold molecular gas. With peak CO(2-1) optical depths of τ=0.88 +0.06−0.06⁠, they include the narrowest and by far the deepest absorption of this type which has been observed to date in a brightest cluster galaxy. By comparing the relative strengths of the lines for the most strongly absorbing region, we are able to estimate a gas temperature of 42+25−11 K and line-of-sight column densities of NCO=2+3−1×1017cm−2 and NH2=7+10−4×1020cm−2⁠.

Item Type:Article
Full text:(AM) Accepted Manuscript
Download PDF
Full text:(VoR) Version of Record
Download PDF
Publisher Web site:
Publisher statement:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
Date accepted:05 February 2019
Date deposited:19 February 2019
Date of first online publication:11 February 2019
Date first made open access:No date available

Save or Share this output

Look up in GoogleScholar