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The GLEAMing of the first supermassive black holes: II. A new sample of high-redshift radio galaxy candidates


Broderick, JW and Drouart, G and Seymour, N and Galvin, TJ and Wright, N and Carnero Rosell, A and Chhetri, R and Dannerbauer, H and Driver, SP and Morgan, JS and Moss, VA and Prabu, S and Afonso, JM and De Breuck, C and Emonts, BHC and Franzen, TMO and Gutierrez, CM and Hancock, PJ and Heald, GH and Hurley-Walker, N and Ivison, RJ and Lehnert, MD and Noirot, G and Read, M and Shabala, SS and Stern, D and Sutherland, WJ and Sutorius, E and Turner, RJ and Vernet, J, The GLEAMing of the first supermassive black holes: II. A new sample of high-redshift radio galaxy candidates, Publications of the Astronomical Society of Australia, 39, (2022) Article 061. ISSN 1448-6083 (2022) [Refereed Article]

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DOI: doi:10.1017/pasa.2022.42


While unobscured and radio-quiet active galactic nuclei are regularly being found at redshifts z>6, their obscured and radio-loud counterparts remain elusive. We build upon our successful pilot study, presenting a new sample of low-frequency-selected candidate high-redshift radio galaxies (HzRGs) over a sky area 20 times larger. We have refined our selection technique, in which we select sources with curved radio spectra between 72231 MHz from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. In combination with the requirements that our GLEAM-selected HzRG candidates have compact radio morphologies and be undetected in near-infrared Ks -band imaging from the Visible and Infrared Survey Telescope for Astronomy Kilo-degree Infrared Galaxy (VIKING) survey, we find 51 new candidate HzRGs over a sky area of approximately 1200 deg2. Our sample also includes two sources from the pilot study: the second-most distant radio galaxy currently known, at z=5.55, with another source potentially at z∼8. We present our refined selection technique and analyse the properties of the sample. We model the broadband radio spectra between 74 MHz and 9 GHz by supplementing the GLEAM data with both publicly available data and new observations from the Australia Telescope Compact Array at 5.5 and 9 GHz. In addition, deep Ks -band imaging from the High-Acuity Widefield K-band Imager (HAWK-I) on the Very Large Telescope and from the Southern Herschel Astrophysical Terahertz Large Area Survey Regions Ks -band Survey (SHARKS) is presented for five sources. We discuss the prospects of finding very distant radio galaxies in our sample, potentially within the epoch of reionisation at z≳6.5.

Item Details

Item Type:Refereed Article
Keywords:galaxies: high-redshift, galaxies: active, radio continuum: galaxies, infrared: galaxies
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Cosmology and extragalactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Shabala, SS (Associate Professor Stas Shabala)
UTAS Author:Turner, RJ (Dr Ross Turner)
ID Code:154482
Year Published:2022
Deposited By:Physics
Deposited On:2022-12-03
Last Modified:2023-01-12

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