AT20GHARC ivo://nasa.heasarc/at20gharc NASA/GSFC HEASARC Chhetri et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source This table contains the high-angular-resolution catalog for the Australia Telescope 20-GHz (AT20G) survey, using the high-angular-resolution 6-km antenna data at the baselines of ~4500 m of the Australia Telescope Compact Array (ATCA). The authors have used the data to produce the visibility catalog that separates the compact active galactic nuclei (AGNs) from the extended radio sources at the 0.15-arcsecond angular scale, corresponding to the linear size scale of 1 kpc at redshifts higher than 0.7. They find the radio population at 20 GHz to be dominated by compact AGNs constituting 77% of the total sources in the AT20G. In the paper, they introduce the visibility-spectra diagnostic plot, produced using the AT20G cross-matches with lower frequency radio surveys at 1 GHz [the NRAO VLA Sky Survey (NVSS: Condon et al. 1998, AJ, 115, 1693) and the Sydney University Molonglo Sky Survey (SUMSS: Mauch et al. 2003, MNRAS, 342, 1117)], that separates the 20-GHz population into distinct sub-populations of the compact AGNs, the compact steep-spectrum (CSS) sources, the extended AGN-powered sources and extended flat-spectrum sources. The extended flat-spectrum sources include a local thermal emitting population of high-latitude planetary nebulae and also gravitational lens and binary black hole candidates among the AGNs. The authors find a smooth transition in properties between the CSS sources and the AGN populations. The visibility catalog, together with the main AT20G survey, provides an estimate of angular size scales for sources in the AT20G and an estimate of the flux arising from central cores of extended radio sources. The identification of the compact AGNs in the AT20G survey provides high-quality calibrators for high-frequency radio telescope arrays and very large baseline interferometry observations. This table was created by the HEASARC in December 2013 based on machine-readable versions of Tables 2 and 3 from the reference paper which were obtained from the MNRAS web site. This is a service provided by NASA HEASARC . 2013MNRAS.434..956C https://heasarc.gsfc.nasa.gov/W3Browse/all/at20gharc.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=at20gharc& GET text/xml 180 99999 true 192.748875 -88.69966667 0.0833333333333333 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=at20gharc GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_at20gharc&Action=More+Options&Action=Parameter+Search&ConeAdd=1 RADIO CATALOG 0.0833333333333333 Radio public at20gharc Australia Telescope 20-GHz (AT20G) High-Angular Resolution Catal name Source Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable flux_20_ghz Flux Density at 20 GHz mJy phot.flux.density;em.radio.12-30GHz int nullable flux_8p6_ghz Flux Density at 8.6 GHz mJy phot.flux.density;em.radio.6-12GHz int nullable flux_4p8_ghz Flux Density at 4.8 GHz mJy phot.flux.density;em.radio.3-6GHz int nullable flux_1p4_ghz Flux Density at 1.4 GHz mJy phot.flux.density;em.radio.750-1500MHz int nullable vis_1 First 6-km Visibility obs.param double nullable vis_2 Second 6-km Visibility obs.param double nullable vis_error Uncertainty in All the 6-km Visibilities stat.error;obs.param double nullable vis_8 Eighth 6-km Visibility obs.param double nullable alpha_8p6_20_ghz Spectral Index Between 8.6 and 20 GHz spect.index;em.radio.6-12GHz;phot.flux.density;em.radio.12-30GHz double nullable vis_7 Seventh 6-km Visibility obs.param double nullable vis_4 Fourth 6-km Visibility obs.param double nullable bii Galactic Latitude degree pos.galactic.lat double nullable source_flags Flags with Further Information Concerning Source meta.code;src char nullable alpha_4p8_8p6_ghz Spectral Index Between 4.8 and 20 GHz spect.index;em.radio.3-6GHz;phot.flux.density;em.radio.6-12GHz double nullable flux_0p8_ghz Flux Density at 0.8 GHz mJy phot.flux.density;em.radio.750-1500MHz int nullable alpha_1_20_ghz Spectral Index Between 1 and 20 GHz spect.index;em.radio.750-1500MHz;phot.flux.density;em.radio.12-30GHz double nullable vis_6 Sixth 6-km Visibility obs.param double nullable alpha_1_8p6_ghz Spectral Index Between 1 and 8.6 GHz spect.index;em.radio.750-1500MHz;phot.flux.density;em.radio.6-12GHz double nullable lii Galactic Longitude degree pos.galactic.lon double nullable alpha_4p8_20_ghz Spectral Index Between 4.8 and 20 GHz spect.index;em.radio.3-6GHz;phot.flux.density;em.radio.12-30GHz double nullable vis_3 Third 6-km Visibility obs.param double nullable alpha_1_4p8_ghz Spectral Index Between 1 and 4.8 GHz spect.index;em.radio.750-1500MHz;phot.flux.density;em.radio.3-6GHz double nullable vis_5 Fifth 6-km Visibility obs.param double nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable