AT20G1FGL ivo://nasa.heasarc/at20g1fgl NASA/GSFC HEASARC Mahony et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source The high-frequency radio sky, like the gamma-ray sky surveyed by the Fermi satellite, is dominated by flat-spectrum radio quasars and BL Lac objects at bright flux levels. To investigate the relationship between radio and gamma-ray emission in extragalactic sources, the authors have cross-matched the Australia Telescope 20-GHz survey catalog (AT20G: Murphy et al. 2010, MNRAS, 402, 2403, available as a HEASARC Browse table) with the Fermi-LAT 1-year Point Source Catalog (1FGL: Abdo et al. 2010, ApJS, 188, 405, also available as the HEASARC Browse table FERMILPSC). The 6.0 sr of sky covered by both catalogs (Declination < 0 degrees, |b| > 1.5 degrees) contains 5890 AT20G radio sources and 604 1FGL gamma-ray sources. The AT20G source positions are accurate to within ~1 arcsec and, after excluding known Galactic sources, 43% of Fermi 1FGL sources have an AT20G source within the 95% Fermi confidence ellipse. Monte Carlo tests imply that at least 95% of these matches are genuine associations. Only five gamma-ray sources (1% of the Fermi catalog) have more than one AT20G counterpart in the Fermi error box. The AT20G matches also generally support the active galactic nucleus (AGN) associations in the First LAT AGN Catalog. The authors find a trend of increasing gamma-ray flux density with 20 GHz radio flux density. The Fermi detection rate of AT20G sources is close to 100% for the brightest 20 GHz sources, decreasing to 20% at 1 Jy, and to roughly 1% at 100 mJy. Eight of the matched AT20G sources have no association listed in 1FGL and are presented here as potential gamma-ray AGNs for the first time. The authors also identify an alternative AGN counterpart to one 1FGL source. The percentage of Fermi sources with AT20G detections decreases toward the Galactic plane, suggesting that the 1FGL catalog contains at least 50 Galactic gamma-ray sources in the southern hemisphere that are yet to be identified. This table contains the complete list of all 233 Fermi-AT20G matches. This table was created by the HEASARC in August 2010 based on the electronic version of Table 4 obtained from the ApJ web site. This is a service provided by NASA HEASARC . 2010ApJ...718..587M https://heasarc.gsfc.nasa.gov/W3Browse/all/at20g1fgl.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=at20g1fgl& GET text/xml 180 99999 true 156.64020833 -85.72097222 0.166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=at20g1fgl GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_at20g1fgl&Action=More+Options&Action=Parameter+Search&ConeAdd=1 RADIO CATALOG 0.166666666666667 Gamma-ray Radio public at20g1fgl AT20G/Fermi 1FGL Source Catalog name AT20G Source Designation (AT20G JHHMMSS-DDMMSS) 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_1p5_cm Flux Density at 20 GHz mJy phot.flux.density;em.radio.12-30GHz int nullable fermi_name Fermi Source Designation meta.id.assoc char nullable fermi_ra Right Ascension of Fermi Source degree pos.eq.ra;em.gamma.hard double nullable fermi_dec Declination of Fermi Source degree pos.eq.dec;em.gamma.hard double nullable fermi_flux_density Differential Gamma-Ray Flux Density at the Pivot Energy cm^-2/MeV/s phot.flux.density;em.gamma.hard double nullable fermi_flux_density_error Uncertainty in Flux Density cm^-2/MeV/s stat.error;phot.flux.density;em.gamma.hard 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 bii Galactic Latitude degree pos.galactic.lat double nullable ref_redshift Reference for Redshift meta.ref;src.redshift char nullable fermi_variability_index Gamma-Ray Variability Index src.var.index double nullable optical_dec Declination of Optical Source degree pos.eq.dec;em.opt double nullable alt_name Fermi Association in 1FGL meta.id.assoc char nullable fermi_pivot_energy Pivot Energy (MeV) MeV phys.energy double nullable bj_mag SuperCOSMOS B_J Band Magnitude mag phot.mag;em.opt.B double nullable flux_3p5_cm Flux Density at 8.4 GHz mJy phot.flux.density;em.radio.6-12GHz short nullable flux_30_cm Flux Density at 1 GHz mJy phot.flux.density;em.radio.750-1500MHz int nullable off_set Offset Between Fermi and AT20G Positions degree pos.angDistance;em.radio;em.gamma.hard double nullable lii Galactic Longitude degree pos.galactic.lon double nullable redshift Redshift src.redshift double nullable fermi_source_type Classification in 1FGL src.class char nullable fermi_position_angle_95 The 95%-Confidence Position Angle degree pos.posAng;pos.errorEllipse double nullable fermi_semi_major_axis_95 The 95%-Confidence Semi-Major Axis degree phys.size.smajAxis;pos.errorEllipse double nullable alt_gammaray_name Fermi Bright Source Catalog Source Identification meta.id.assoc char nullable fermi_semi_minor_axis_95 The 95%-Confidence Semi-Minor Axis degree phys.size.sminAxis;pos.errorEllipse double nullable flux_6_cm Flux Density at 4.8 GHz mJy phot.flux.density;em.radio.3-6GHz short nullable optical_ra Right Ascension of Optical Source degree pos.eq.ra;em.opt double nullable radio_spectral_index Spectral Index Between 4.8 and 20 GHz spect.index;em.radio double nullable at20g_quality_flag AT20G Flux Quality Flag meta.code.qual char nullable