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

Tom Rose, A. C. Edge, F. Combes, S. Hamer, B. R. McNamara, H. Russell, M. Gaspari, P. Salomé, C. Sarazin, G. R. Tremblay, S. A. Baum, M. N. Bremer, M. Donahue, A. C. Fabian, G. Ferland, N. Nesvadba, C. O'Dea, J. B. R. Oonk, A. B. Peck

Research output: Contribution to journalArticle (Academic Journal)peer-review

23 Downloads (Pure)


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.
Original languageEnglish
Pages (from-to)364-380
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society, Advance Access
Issue number1
Early online date28 May 2020
Publication statusPublished - 1 Jul 2020


  • galaxies: clusters: individual: Hydra-A
  • galaxies: clusters: general
  • radio continuum: galaxies
  • radio lines: interstellar medium

Fingerprint Dive into the research topics of 'A molecular absorption line survey toward the AGN of Hydra-A'. Together they form a unique fingerprint.

Cite this