The Australia Telescope 20 GHz Survey: the source catalogue

Abstract

We present the full source catalogue from the Australia Telescope 20 GHz (AT20G) Survey. The AT20G is a blind radio survey carried out at 20 GHz with the Australia Telescope Compact Array (ATCA) from 2004 to 2008, and covers the whole sky south of declination 0 • . The AT20G source catalogue presented here is an order of magnitude larger than any previous catalogue of high-frequency radio sources, and includes 5890 sources above a 20 GHz flux-density limit of 40 mJy. All AT20G sources have total intensity and polarization measured at 20 GHz, and most sources south of declination −15 • also have near-simultaneous flux-density measurements at 5 and 8 GHz. A total of 1559 sources were detected in polarized total intensity at one or more of the three frequencies.The completeness of the AT20G source catalogue is 91 per cent above 100 mJy beam −1 and 79 per cent above 50 mJy beam −1 in regions south of declination −15 • . North of −15 • , some observations of sources between 14 and 20 h in right ascension were lost due to bad weather and could not be repeated, so the catalogue completeness is lower in this region. Each detected source was visually inspected as part of our quality control process, and so the reliability of the final catalogue is essentially 100 per cent.We detect a small but significant population of non-thermal sources that are either undetected or have only weak detections in low-frequency catalogues. We introduce the term Ultra-Inverted Spectrum to describe these radio sources, which have a spectral index α(5, 20) > +0.7 and which constitute roughly 1.2 per cent of the AT20G sample.

Hi absorption in nearby compact radio galaxies

“…Targets were selected at 20 GHz from the AT20G survey catalogue (Murphy et al 2010), which were cross-matched with the 6dF Galaxy Survey (Jones et al 2009) to obtain redshift information (Sadler et al 2014). In order to select compact sources, those with extended radio emission on scales greater than 15 arcseconds at 20 GHz were removed.…”

“…Column (4): The AT20G 20 GHz flux density (Murphy et al 2010). Column (5): S1.4 is the NVSS 1.4 GHz flux density (Condon et al 1998).…”

“…Fig. 1 shows the spectral indices from the AT20G survey (Murphy et al 2010) for 49 of our sources with flux measurements at 20 GHz, 8.4 GHz and 4.8 GHz. Considering only these flux measurements, the majority have flat spectral indices.…”

“…give an upper limit for T spin given N H,X and assuming a covering factor of f = 1 (Section 4.2); Γ is the measured photon index of the X-ray spectra; L 5GHz the luminosity at 5 GHz (from the AT20G flux; Murphy et al 2010); L X the X-ray luminosity, and log 10 (L X /L 5GHz ) the logarithmic ratio of the X-ray and 5 GHz luminosities. A value of log 10 (L X /L 5GHz ) < 1.8 matches with observed values for FR-I sources (Tengstrand et al 2009), suggesting these may be FR-I radio galaxies, or GPS sources for which we haven't yet observed a turnover in the spectrum at lower frequencies.…”

“…Here we present the results of the search of Hi absorption complementrary to Allison et al (2012a), who searched for Hi in 29 targets as part of a sample of 66 nearby (0.04 < z < 0.08) compact sources selected from the Australia Telescope 20 GHz survey (AT20G; Murphy et al 2010), with the Australian Telescope Compact Array (ATCA) on the Broadband Backend (CABB). A total of three detections were made by Allison et al (2012a), two of which were previously unknown.…”