J/A+A/713/A139ivo://CDS.VizieR/J/A+A/713/A139CDSMazzolari G.Gilli R.Mignoli M.Brusa M.Prandoni I.Vito F.,Delvecchio I.Lanzuisi G.Peca A.Comastri A.Marchesi S.Chiaberge M.,Brienza M.Vignali C.Signorini M.D'Amato Q.Gentile F.Iwasawa K.,Norman C.Traina A.Loiacono F.Baldini P.Annunziatella M.Decarli R.2026-09-15T17:43:34Z2026-09-15T18:43:04ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fractive-galactic-nucleiradio-sourcesredshiftedModels of supermassive black holes (SMBHs) and galaxy coevolution, simulations, and recent JWST observations suggest that the population of heavily obscured, Compton-thick (CTK) active galactic nuclei (AGNs) at high redshift might be underestimated by X-ray surveys. To retrieve a complete census of SMBHs it is therefore necessary to identify new and complementary methods to select these sources, for example by exploiting the radio band as radio waves are almost unaffected by obscuration. We aim to test the effectiveness of radio selection to discover heavily obscured AGNs, particularly at high z, and, in turn, measure their abundance for the first time from a radio perspective. We considered the radio sources detected in the J1030 field, which is one of the fields with the deepest combination of 1.4GHz radio and X-ray observations publicly available. We defined a radio excess parameter as the ratio between the star formation rate (SFR) that would correspond to the observed radio luminosity and the one directly derived from the spectral-energy-distribution (SED) fitting, REX=SFR_1.4GHz_/SFR^corr^_SED_. We then selected sources with REX>8.5 as radio- excess AGNs; this corresponds to a 3{sigma} excess above the median value (REX~1). In this way, we find 145 radio-excess sources falling in the Chandra X-ray image footprint but without X-ray detection. From the deep X-ray upper limits, we estimated a lower limit to the obscuration of each radio- excess AGN, finding on average log(N_H_/m{cm^-2^)>23.7. A CTK AGN scenario is also supported by the results of the X-ray stacking analysis performed on sources at z>1.5, which revealed X-ray luminosities and hardness ratios compatible with very highly obscured AGNs. Finally, we computed the number density of these radio-selected CTK AGNs. While at z~2 the radio number density agrees well with the CTK AGN predictions of different population synthesis models, at z~3 the radio selection returns a CTK AGN number density ~2-3 times larger than what is predicted by the CXB models and X-ray observations. This result supports the effectiveness of radio emission in selecting the most obscured sources, unraveling a population of AGNs potentially missed by X-ray surveys at z>3; this paves the way to a synergistic use of the future radio and X-ray facilities such as the Square Kilometer Array Observatory (SKAO), NewAthena, and the Advanced X-ray Imager Satellite (AXIS).2026A&A...713A.139Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/713/A139CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/637/A52 : Deep Chandra survey in J1030+0524 field (Nanni+, 2020)J/A+A/668/A133 : Deep 1.4GHz survey of the J1030 field (D'Amato+, 2022)J/A+A/676/A49 : J1030+0524 field spectral catalog (Signorini+, 2023)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/713/A139https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/713/A139http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/713/A139https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/713/A139https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/713/A139http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/713/A139GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/713/A139/rextable (Catalog of radio sources)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/713/A139/rextable?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/713/A139/rextable?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/713/A139/rextable?GETtext/xml+votable180.050000true157.799235.350460.0055555555555555566/27440https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/713/A139?format=asciiRadiodefaultJ/A+A/713/A139/rextableCatalog of radio sourcesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDradRadio ID taken from D'Amato et al. (2022A&A...668A.133D, Cat. J/A+A/668/A133)meta.id;meta.mainintIDKID of the counterpart in the Ks-band selected catalog (taken from Mignoli et al., in prep) (1)meta.idintRAJ2000Right ascension (J2000) of the optical counterpartdegpos.eq.ra;meta.mainDEJ2000Declination (J2000) of the optical counterpartdegpos.eq.dec;meta.mainzRedshift (2)src.redshiftfloatb_zLower value of the redshift derived from +/-1 sigma error around the best value (For spectroscopic redshift b_z=z)stat.error;src.redshift;stat.minfloatB_zUpper value of the redshift derived from +/-1 sigma error around the best value (For spectroscopic redshift B_z=z)stat.error;src.redshift;stat.maxfloatf_z[0/1] Flag indicating if the source has a spectroscopic redshift, spec-z: 1, photo-z: 0meta.codeintSFRoptStar formation rate derived from CIGALE SED-fittingsolMass/yrphys.SFRfloatlogMstarlog10 of the stellar mass derived from CIGALE SED-fittinglog(solMass)phys.massfloatlogLradlog10 of the 1.4GHz luminositylog(1e-07W)phys.luminosity;em.radio.750-1500MHzfloatSFRradSFR derived from the radio luminositysolMass/yrphys.SFRdoubleREXRadio excess parameter valuestat.fit.paramfloatf_REX[0/1] Flag indicating if the source is classified as radio excess (REX>8.5), radio excess: 1, non radio excess: 0meta.codeintfRL[0/1] Flag indicating if the source is classified as radio loud AGN, RLAGN: 1, RQAGN: 0meta.codeintXIDX-ray ID taken from Nanni et al. (2020A&A...637A..52N, Cat. J/A+A/637/A52) (3)meta.idintlogNH? log10 of the hydrogen column density for REX sources (4)log(cm**-2)phys.columnDensityfloatnullablef_logNH[-1/1]? Flag on logNH (5)meta.codeintnullable