1. ATCA detections of massive molecular gas reservoirs in dusty, high-z radio galaxies.
- Author
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Heywood, I., Contreras, Y., Smith, D. J. B., Cooray, A., Dunne, L., Gómez, L., Ibar, E., Ivison, R. J., Jarvis, M. J., Michałowski, M. J., Riechers, D. A., and van der Werf, P.
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ASTRONOMICAL observations , *GALACTIC redshift , *RADIO galaxies , *GAS reservoirs , *TELESCOPES , *SPECTRUM analysis - Abstract
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-Astrophysical Terahertz Large Area Survey suggest high levels of dust (>109 M⊙) and a correspondingly large amount of obscured star formation (~1000 M⊙ yr-1). The molecular gas is traced via the J = 1 → 0 transition of 12CO, its luminosity implying total H2 masses of (1.7 ± 0.3) × 1011 and (9.5 ± 2.4) × 1010 (aCO/0.8) M⊙ in HATLAS J090426.9+015448 and HATLAS J140930.4+003803, respectively. Both galaxies exhibit molecular line emission over a broad (~1000 km s-1) velocity range and feature double-peaked profiles. We interpret this as evidence of either a large rotating disc or an on-going merger. Gas depletion time-scales 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. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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