Radio loudness and classification for radio source J/PASJ/73/313 ivo://CDS.VizieR/J/PASJ/73/313 doi:10.26093/cds/vizier/bj-29-9s CDS Zhang L. Fan J. Zhu J. 2026-03-17T20:05:54Z 2021-10-01T13:32:07Z CDS support team CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France cds-question@unistra.fr active-galactic-nuclei bl-lacertae-objects quasars The extragalactic radio sources are divided into two subclasses (radio-loud and radio-quiet sources) in the literature using radio loudness (R), which is defined as the ratio of radio emission to optical emission, but the boundary R-value separating the two classes is different in various sources. In this work, a sample of 2419 objects from the 13th catalog of quasars and active nuclei is used to build a boundary for the two subclasses. To do so, we compiled the radio and optical data, calculated their radio and optical indexes, made K-correction, obtained the radio loudness, and adopted a Bayesian analysis method to the logarithm of radio loudness for classification. We also investigated the correlations of radio loudness with radio/optical luminosities. Our main conclusions are summarized as follows: (1) The distribution of the logarithm of radio loudness (log R) is bimodal, the sources with log R<1.26 are classified as radio-quiet sources, and those with log R>1.26 are classified as radio-loud ones from the Bayesian analysis method. (2) The average radio-optical effective spectral index of radio-quiet sources is <RO>=0.05, while that of radio-loud sources is <{alpha}_RO_>=0.55. (3) There are positive correlations between radio luminosity and radio loudness for both radio-loud sources and radio-quiet sources. (4) A dividing line of separating the distribution of the clusters on the diagram of radio loudness against radio luminosity was obtained statistically to set the boundary between radio-loud sources and radio-quiet sources, with an accuracy of 99.73% based on the classification result from the Bayesian analysis method. 2021PASJ...73..313Z https://cdsarc.cds.unistra.fr/viz-bin/cat/J/PASJ/73/313 Catalog Research IsServedBy TAP VizieR generic service IsServedBy Conesearch service related-to VII/258 : Quasars and Active Galactic Nuclei (13th Ed.) 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Should Not be used for identification. meta.record int Name Source name meta.id;meta.main char GLON ? Galactic longitude deg pos.galactic.lon nullable GLAT ? Galactic latitude deg pos.galactic.lat nullable CL [A BL Q] Type (1) src.class char z ? Redshift src.redshift float nullable F6 ? Radio flux density at 6cm Jy phot.flux.density;em.radio.3-6GHz float nullable F20 ? Radio flux density at 20cm Jy phot.flux.density;em.radio.750-1500MHz float nullable Vmag ? V magnitude mag phot.mag;em.opt.V float nullable B-V ? B-V colour index mag phot.color;em.opt.B;em.opt.V float nullable U-B ? U-B colour index mag phot.color;em.opt.U;em.opt.B float nullable Jmag ? J magnitude mag phot.mag;em.IR.J float nullable Hmag ? H magnitude mag phot.mag;em.IR.H float nullable Kmag K magnitude mag phot.mag;em.IR.K float aR ? Radio spectral index, {alpha}_R_ spect.index float nullable aO ? Optical spectral index, {alpha}_O_ spect.index float nullable e_aO rms uncertainty on aO stat.error float aRO Radio-optical effective spectral index, {alpha}_RO_ spect.index float logR ? Radio loudness phot.flux;arith.ratio float nullable e_logR ? rms uncertainty on logR stat.error float nullable logLR ? Radio luminosity at 6cm phys.luminosity float nullable logLO ? optical luminosity at the B band phys.luminosity;em.opt float nullable Mod [RL RQ] Classification mode from Bayesian analysis method (2) meta.code.class char _RA.icrs Right ascension (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services) deg pos.eq.ra nullable indexed _DE.icrs Declination (ICRS) (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services) deg pos.eq.dec nullable indexed