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Gas-rich mergers and feedback are ubiquitous amongst starbursting radio galaxies, as revealed by the VLA, IRAM PdBI and Herschel.

Ivison, R.J. and Smail, I. and Amblard, A. and Arumugam, V. and De Breuck, C. and Emonts, B.H.C. and Feain, I. and Greve, T.R. and Haas, M. and Ibar, E. and Jarvis, M.J. and Kovács, A. and Lehnert, M.D. and Nesvadba, N.P.H. and Röttgering, H.J.A. and Seymour, N. and Wylezalek, D. (2012) 'Gas-rich mergers and feedback are ubiquitous amongst starbursting radio galaxies, as revealed by the VLA, IRAM PdBI and Herschel.', Monthly notices of the Royal Astronomical Society., 425 (2). pp. 1320-1331.


We report new, sensitive observations of two z ˜ 3-3.5 far-infrared-luminous radio galaxies, 6C 1909+72 and B3 J2330+3927, in the 12CO J = 1-0 transition with the Karl Jansky Very Large Array and at 100-500 m using Herschel, alongside new and archival 12CO J = 4-3 observations from the Plateau de Bure Interferometer. We introduce a new colour-colour diagnostic plot to constrain the redshifts of several distant, dusty galaxies in our target fields. A bright SMG near 6C 1909+72 likely shares the same node or filament as the signpost active galactic nuclei (AGN), but it is not detected in 12CO despite ˜20 000 km s-1 of velocity coverage. Also in the 6C 1909+72 field, a large, red dust feature spanning ≈500 kpc is aligned with the radio jet. We suggest several processes by which metal-rich material may have been transported, favouring a collimated outflow reminiscent of the jet-oriented metal enrichment seen in local cluster environments. Our interferometric imaging reveals a gas-rich companion to B3 J2330+3927; indeed, all bar one of the eight z ≳ 2 radio galaxies (or companions) detected in 12CO provide some evidence that starburst activity in radio-loud AGN at high redshift is driven by the interaction of two or more gas-rich systems in which a significant mass of stars has already formed, rather than via steady accretion of cold gas from the cosmic web. We find that the 12CO brightness temperature ratios in radio-loud AGN host galaxies are significantly higher than those seen in similarly intense starbursts where AGN activity is less pronounced. Our most extreme example, where L CO 4-3'/L CO 1-0'>2.7, provides evidence that significant energy is being deposited rapidly into the molecular gas via X-rays and/or mechanical ('quasar-mode') feedback from the AGN, leading to a high degree of turbulence globally and a low optical depth in 12CO - feedback that may lead to the cessation of star formation on a time-scale commensurate with that of the jet activity, ≲10 Myr.

Item Type:Article
Keywords:Galaxies, Active, High-redshift, Starburst, Infrared, Radio lines.
Full text:(NA) Not Applicable
Download PDF (arXiv version)
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Publisher statement:The definitive version is available at
Date accepted:No date available
Date deposited:No date available
Date of first online publication:September 2012
Date first made open access:No date available

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