AT20GBSPOL ivo://nasa.heasarc/at20gbspol NASA/GSFC HEASARC Massardi et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source This table contains polarization data for 180 extragalactic sources extracted from the Australia Telescope 20-GHz (AT20G) survey catalog and observed with the Australia Telescope Compact Array (ATCA) during a dedicated, high sensitivity run (sigma<sub>P</sub> ~ 1 mJy). For the sake of completeness, the authors extracted the polarization information for seven extended sources from the 9-yr Wilkinson Microwave Anisotropy Probe co-added maps at 23 GHz. The full sample of 187 sources constitutes a ~ 99% complete sample of extragalactic sources brighter than S<sub>20GHz</sub> = 500 mJy at the selection epoch with Declination below -30<sup>o</sup>. The sample has a 91.4% detection rate in polarization at ~ 20 GHz (94% if considering the sub-sample of point-like sources). The authors have measurements also at 4.8 and 8.6 GHz within ~1 month of the 20-GHz observations for 172 sources so as to reconstruct the spectral properties of the sample in total intensity and in polarization: 143 of them have a polarization detection at all three frequencies. The authors find that there is no statistically significant evidence of a relationship either between the fraction of polarization and frequency or between the fraction of polarization and the total intensity flux density. This indicates that Faraday depolarization is not very important above 4.8 GHz and that the magnetic field is not substantially more ordered in the regions dominating the emission at higher frequencies (up to 20 GHz). The authors estimate the distribution of the polarization fraction and the polarized flux density source counts at ~20 GHz. The selection of the sample was based on the list of confirmed AT20G sources available at the epoch of these observations (2006 October). The authors selected all objects with flux density S<sub>20GHz</sub> > 500 mJy and Declination below -30<sup>o</sup>, excluding the Galactic plane region (|b| <= 1.5o^) and the Large Magellanic Cloud (LMC) region (inside a circle of 5.5<sup>o</sup> radius centered at RA =05:23:34.7 and Dec=-69:45:22 in J2000.0 coordinates). This resulted in a complete sample of 189 sources. The observations were taken on October 1, 2006 using the most compact hybrid configuration of ATCA, H75, excluding the data from the farthest antenna. The longest baseline of this configuration is 75 m, and its T-shape ensures adequate Fourier coverage for snapshots taken on a relatively small range of hour angles and at high elevation. In a number of cases, indicated by source_flags values of 's', 'f' or 'w', the highest frequency data is not at 18 GHz, but at 20 or 23 GHz. This table was created by the HEASARC in January 2015 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/436/2915">CDS Catalog J/MNRAS/436/2915</a> file table2.dat. This is a service provided by NASA HEASARC . 2010MNRAS.402.2403M https://heasarc.gsfc.nasa.gov/W3Browse/all/at20gbspol.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=at20gbspol& GET text/xml 180 99999 true 178.22383333 -83.73627778 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=at20gbspol GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_at20gbspol&Action=More+Options&Action=Parameter+Search&ConeAdd=1 RADIO CATALOG 0.0166666666666667 Radio public at20gbspol Bright Extra-Galactic AT20G Sources Polarizations Catalog name Source Designation (AT20G JHHMMSS+DDMMSS or Fornax A) 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_18_ghz 18-GHz Scalar Average Flux Density mJy phot.flux.density;em.radio.12-30GHz double nullable flux_18_ghz_error RMS Uncertainty in 18-GHz Scalar Average Flux Density mJy stat.error;phot.flux.density;em.radio.12-30GHz double nullable pol_flux_18_ghz_limit Limit Flag for Polarized Flux Density at 18 GHz meta.code;phot.flux.density;em.radio.12-30GHz char nullable pol_flux_18_ghz Polarized Flux Density at 18 GHz mJy phot.flux.density;em.radio.12-30GHz double nullable pol_flux_18_ghz_error RMS Uncertainty in Polarized Flux Density at 18 GHz mJy stat.error;phot.flux.density;em.radio.12-30GHz double nullable source_flags Flag(s) [sfbwc] Indicate Notes Concerning Sources meta.code;src char nullable pol_flux_4p8_ghz_limit Limit Flag for Polarized Flux Density at 4.8 GHz meta.code;phot.flux.density;em.radio.3-6GHz char nullable bii Galactic Latitude degree pos.galactic.lat double nullable pol_flux_4p8_ghz_error RMS Uncertainty in Polarized Flux Density at 4.8 GHz mJy stat.error;phot.flux.density;em.radio.3-6GHz double nullable frac_pol_4p8_ghz Polarization Degree at 4.8 GHz percent phys.polarization;em.radio.6-12GHz double nullable at20g_ls_vis_ratio Ratio Between the Visibilities Amplitudes obs.param;arith.ratio double nullable frac_pol_4p8_ghz_error RMS Uncertainty in Polarization Degree at 4.8 GHz percent stat.error;phys.polarization;em.radio.6-12GHz double nullable frac_pol_8p6_ghz_error RMS Uncertainty in Polarization Degree at 8.6 GHz percent stat.error;phys.polarization;em.radio.6-12GHz double nullable pol_flux_8p6_ghz_error RMS Uncertainty in Polarized Flux Density at 8.6 GHz mJy stat.error;phot.flux.density;em.radio.6-12GHz double nullable flux_4p8_ghz_error RMS Uncertainty in Total Intensity Flux Density at 4.8 GHz mJy stat.error;phot.flux.density;em.radio.3-6GHz double nullable pol_flux_4p8_ghz Polarized Flux Density at 4.8 GHz mJy phot.flux.density;em.radio.3-6GHz double nullable frac_pol_18_ghz_error RMS Uncertainty in Fractional Polarization at 18 GHz percent stat.error;phys.polarization;em.radio.12-30GHz double nullable pol_angle_8p6_ghz Polarization Angle at 8.6 GHz degree pos.posAng;phys.polarization;em.radio.6-12GHz double nullable flux_8p6_ghz_error RMS Uncertainty in Total Intensity Flux Density at 8.6 GHz mJy stat.error;phot.flux.density;em.radio.6-12GHz double nullable lii Galactic Longitude degree pos.galactic.lon double nullable pol_flux_8p6_ghz_limit Limit Flag for Polarized Flux Density at 8.6 GHz meta.code;phot.flux.density;em.radio.6-12GHz char nullable pol_angle_4p8_ghz Polarization Angle at 4.8 GHz degree pos.posAng;phys.polarization;em.radio.6-12GHz double nullable frac_pol_18_ghz Fractional Polarization at 18 GHz percent phys.polarization;em.radio.12-30GHz double nullable flux_8p6_ghz Total Intensity Flux Density at 8.6 GHz mJy phot.flux.density;em.radio.6-12GHz double nullable flux_4p8_ghz Total Intensity Flux Density at 4.8 GHz mJy phot.flux.density;em.radio.3-6GHz double nullable pol_flux_8p6_ghz Polarized Flux Density at 8.6 GHz mJy phot.flux.density;em.radio.6-12GHz double nullable pol_angle_18_ghz Polarization Angle at 18 GHz degree pos.posAng;phys.polarization;em.radio.12-30GHz double nullable frac_pol_8p6_ghz Polarization Degree at 8.6 GHz percent phys.polarization;em.radio.6-12GHz 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