Radio sources at 6~>z~>4 with ASKAP in G23J/MNRAS/519/4902ivo://CDS.VizieR/J/MNRAS/519/4902CDSShobhana D.Norris R.P.Filipovic M.D.Barnes L.A.Hopkins A.M.,Prandoni I.Brown M.J.I.Shabala S.S.2026-04-21T14:45:49Z2026-04-21T15:44:18ZCDS support teamCDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, Francecds-question@unistra.frgalaxiesactive-galactic-nucleiquasarsradio-sourcesredshiftedspectroscopyphotometryastronomical-object-identificationastrometryvisible-astronomyinfrared-astronomyastronomical-reference-materialsUsing the Lyman Dropout technique, we identify 148 candidate radio sources at z ~> 4-7 from the 887.5 MHz Australian Square Kilometre Array Pathfinder (ASKAP) observations of the GAMA23 field. About 112 radio sources are currently known beyond redshift z ~ 4. However, simulations predict that hundreds of thousands of radio sources exist in that redshift range, many of which are probably in existing radio catalogues, but do not have measured redshifts, either because their optical emission is too faint or because of the lack of techniques that can identify candidate high-redshift radio sources (HzRSs). Our study addresses these issues using the Lyman Dropout search technique. This newly built sample probes radio luminosities that are 1-2 orders of magnitude fainter than known radio-active galactic nuclei (AGN) at similar redshifts, thanks to ASKAP's sensitivity. We investigate the physical origin of radio emission in our sample using a set of diagnostics: (i) radio luminosity at 1.4 GHz, (ii) 1.4 GHz to 3.4 {mu}m flux density ratio, (iii) Far-IR detection, (iv) WISE colour, and (v) SED modelling. The radio/IR analysis has shown that the majority of radio emission in the faint and bright end of our sample's 887.5 MHz flux density distribution originates from AGN activity. Furthermore, ~10 per cent of our sample are found to have a 250 {mu}m detection, suggesting a composite system. This suggests that some high-z radio-AGNs are hosted by SB galaxies in contrast to low-z radio- AGNs, which are usually hosted by quiescent elliptical galaxies.2023MNRAS.519.4902Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/519/4902CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/494/789 : NIR and MIR photometry of known z>=5 quasars (Ross+, 2020)J/MNRAS/474/3875 : Galaxy And Mass Assembly (GAMA): DR3 (Baldry+, 2018)J/MNRAS/455/2731 : Radio galaxies in ZFOURGE/NMBS (Rees+, 2016)J/MNRAS/379/1442 : Multifrequency observations of 9C sources (Waldram+, 2007)J/A+A/634/A1 : NGC 1068 GRAVITY reconstructed image (GRAVITY+, 2020)J/ApJ/858/77 : DEIMOS 10K spectroscopic survey in COSMOS fieldJ/ApJ/847/136 : H{beta} to N2 line fluxes of nearby galaxies (Brown+, 2017)J/ApJ/819/24 : z>4.5 QSOs with SDSS and WISE. I. Opt. spectra (Wang+, 2016)J/ApJ/784/9 : SCUBA-2 high-redshift galaxies sample (Barger+, 2014)J/ApJ/586/794 : Multiwavelength luminosities of galaxies (Bell, 2003)J/ApJS/224/24 : The COSMOS2015 catalog (Laigle+, 2016)J/A+AS/143/303 : Ultra steep spectrum radio sources catalog (De Breuck+ 2000)VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)VII/282 : T-RECS. Tiered Radio Extragalactic Continuum SimulationV/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)II/365 : The CatWISE2020 catalog (updated version 28-Jan-2021)II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/519/4902https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/519/4902http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/519/4902https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/519/4902https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/519/4902http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/519/4902GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/519/4902/table7 (*z ~> 4-6 radio properties from ASKAP and optical/IR phot. from KiDS, VIKING and CATWISE)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/519/4902/table7?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/519/4902/table7?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/519/4902/table7?GETtext/xml+votable180.050000true344.437-31.2030.005555555555555556Cone search capability for table J/MNRAS/519/4902/tablea1 (List of published radio-AGNs known at redshift z => 4)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/519/4902/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/519/4902/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/519/4902/tablea1?GETtext/xml+votable180.050000true232.7086710.825580.005555555555555556Cone search capability for table J/MNRAS/519/4902/tablea2 (*Visually cross-matching SDSS DR12, FIRST and NVSS catalogs to obtain sources at z ~> 4)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/519/4902/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/519/4902/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/519/4902/tablea2?GETtext/xml+votable180.050000true177.0693552.863950.0055555555555555565/4138 11738 6/0 28 821 2170 3074 3366 4105 4120 4168 4326 4339 4686 5115 5121 5130 5170 5201 5255 5266 5425 5443 5458 5493 5563 5606 5630 5709 5841 5935 5992 6055 6124 6219 6372 6415 6934 6969 7301 7343 7360 7378 7942 8202 8286 8392 8590 8626 8711 8726 8777 8869 8903 9293 9394 9621 9635 9735 10002 10318 10334 10466 10512 10598 10677 10694 10885 11130 11153 11161 11252 11429 11440 11461 11605 11845 11937 12563 15578 16044 16544 16546-16547 16896 17105 17651 17812 17818 18077 18176 18209 18809 18851-18852 18883 18988 19036 19088 19202 19217 19676 19756 20313 20390 20433 21839 23072 23102 23211 24724 25141 25817 25969 26098 26221 26262 26568 26816 26837 27023 27222 27367 27495 27968 28023 28260 28322 28527 30131 31456 31629 31689 32436 32457 32683 33324 34271 34512 35002 35831 35952 36466 40326 43628 44713 44833 46151 46553 46555-46556 46558 46566-46567 46571-46573 46575-46576 46578-46579 46581-46585 46587 46589-46591 46870-46871 46875-46877 46879 46899-46901 46908-46909 46911-46912 46914-46917 46919-46921 46923 46925-46929 46931 46933-46934 46936-46938 46940 46945 46947-46949 46951 469615.883949854262862e-25 6.513807192489934e-20https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/519/4902?format=asciiOpticalInfraredRadiodefault
J/MNRAS/519/4902/table7*z ~> 4-6 radio properties from ASKAP and optical/IR phot. from KiDS, VIKING and CATWISErecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintn_ASKAPNotes for redshift subsamples (1)meta.notecharIndexRedshift subsample index number (Index)meta.idintASKAPASKAP designation name as JHHMMSS-DDMMSS (ASKAP)meta.id;meta.maincharRAJ2000Right ascension (J2000) (RA)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (DEC)degpos.eq.dec;meta.mainS887.5ASKAP flux density at 887.5 MHz coresponds to radio continuum data of the G23 field (S887.5)mJyphot.flux.density;em.radio.750-1500MHzfloatumag? KiDs DR4.1 u optical AB magnitude from Kuijken et al. 2019A&A...625A...2K (Mag_u)magphot.mag;em.opt.Ufloatnullablegmag? KiDs DR4.1 g optical AB magnitude from Kuijken et al. 2019A&A...625A...2K (Mag_g)magphot.mag;em.opt.BfloatnullablermagKiDs DR4.1 r optical AB magnitude from Kuijken et al. 2019A&A...625A...2K (Mag_r)magphot.mag;em.opt.RfloatimagKiDs DR4.1 i optical AB magnitude from Kuijken et al. 2019A&A...625A...2K (Mag_i)magphot.mag;em.opt.IfloatZmag? VIKING Z NIR AB magnitude from Wright et al. 2019A&A...625A...2K, Cat. II/383 (Mag_Z)magphot.mag;em.opt.IfloatnullableW1mag? WISE W1 MIR magnitude in vega system from CATWISE2020 of Marocco et al. 2021ApJS..253....8M, Cat. II/365 (W1)magphot.mag;em.IR.3-4umfloatnullableGurkan+22Display the ASKAP radio sources in G23 field of Gurkan et al. (2022MNRAS.512.6104G, Cat. J/MNRAS/512/6104)meta.ref.urlintnullableWright+24Display the ESO KiDS-DR5 multi-band source catalog of Wright et al. (2024A&A...686A.170W, Cat. II/383)meta.ref.urlintnullableMarocco+21Display the CatWISE2020 catalog of Marocco et al. (2021ApJS..253....8M, Cat. II/365)meta.ref.urlintnullable
J/MNRAS/519/4902/tablea1List of published radio-AGNs known at redshift z => 4SimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIndexIndex raw number of the radio-AGN (Index)meta.idintNameThe radio-AGN name (Name)meta.id;meta.maincharRAJ2000Right ascension (J2000) (RA)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (DEC)degpos.eq.dec;meta.mainzRedshift (z)src.redshiftfloatS1.4? Flux density at 1.4 GHz frequency (S_1.4_)mJyphot.flux.density;em.radio.750-1500MHzdoublenullableClassObject class (class) (1)meta.code.classcharAutAuthor's names of the reference paper (Ref)meta.bib.authorcharBibBibcode of the reference papermeta.bib.bibcodecharCatVizier catalog of the reference papermeta.id;meta.datasetcharn_BibRemarks of the reference papermeta.notechar
J/MNRAS/519/4902/tablea2*Visually cross-matching SDSS DR12, FIRST and NVSS catalogs to obtain sources at z ~> 4S1.4? Flux density at 1.4 GHz frequency (S_1.4_)mJyphot.flux.density;em.radio.750-1500MHzdoublenullableClassObject class (class) (1)meta.code.classcharAutAuthor's names of the reference paper (Ref)meta.bib.authorcharBibBibcode of the reference papermeta.bib.bibcodecharCatVizier catalog of the reference papermeta.id;meta.datasetcharn_BibRemarks of the reference papermeta.notecharSimbadNameSimbad column added by the CDSmeta.idcharnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIndexIndex raw number of the radio-AGN (Index)meta.idintNameThe radio-AGN name (Name)meta.id;meta.maincharRAJ2000Right ascension (J2000) (RA)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (DEC)degpos.eq.dec;meta.mainzRedshift (z)src.redshiftfloat