University of Hertfordshire

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From the same journal

By the same authors

ATCA detections of massive molecular gas reservoirs in dusty, high-z radio galaxies

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  • stw2774

    Final published version, 1.11 MB, PDF document

  • I. Heywood
  • Y. Contreras
  • D. J. B. Smith
  • A. Cooray
  • L. Dunne
  • L. Gomez
  • E. Ibar
  • R. J. Ivison
  • M. J. Jarvis
  • M. J. Michalowski
  • D. A. Riechers
  • P. van der Werf
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Original languageEnglish
Pages (from-to)1297-1307
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 27 Oct 2016


Observations using the 7 mm receiver system on the Australia Telescope Compact Array have revealed large reservoirs of molecular gas in two high-redshift radio galaxies: HATLAS J090426.9+015448 (z = 2.37) and HATLAS J140930.4+003803 (z = 2.04). Optically the targets are very faint, and spectroscopy classifies them as narrow-line radio galaxies. In addition to harbouring an active galactic nucleus the targets share many characteristics of sub-mm galaxies. Far-infrared data from Herschel-ATLAS suggest high levels of dust (>10^9 M_solar) and a correspondingly large amount of obscured star formation (~1000 M_solar / yr). The molecular gas is traced via the J = 1-0 transition of 12CO, its luminosity implying total H_2 masses of (1.7 +/- 0.3) x 10^11 and (9.5 +/- 2.4) x 10^10 (alpha_CO/0.8) M_solar in HATLAS J090426.9+015448 and HATLAS J140930.4+003803 respectively. Both galaxies exhibit molecular line emission over a broad (~1000 km/s) velocity range, and feature double-peaked profiles. We interpret this as evidence of either a large rotating disk or an on-going merger. Gas depletion timescales are ~100 Myr. The 1.4 GHz radio luminosities of our targets place them close to the break in the luminosity function. As such they represent `typical' z > 2 radio sources, responsible for the bulk of the energy emitted at radio wavelengths from accretion-powered sources at high redshift, and yet they rank amongst the most massive systems in terms of molecular gas and dust content. We also detect 115 GHz rest-frame continuum emission, indicating a very steep high-radio-frequency spectrum, possibly classifying the targets as compact steep spectrum objects.


This is an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. © 2016 The Authors. First published online October 27, 2016, available online at doi: 10.1093/mnras/stw2774. Published by Oxford University Press on behalf of the Royal Astronomical Society.

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