J/A+A/707/A347ivo://CDS.VizieR/J/A+A/707/A347CDSChen G.Yang W.Ye X.Yuan Y.Feng J.Fan J.2026-04-02T06:28:33Z2026-03-24T11:16:17ZCDS support team

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

cds-question@unistra.frquasarsradio-sourcesvisible-astronomyspectroscopyThe Fermi Gamma-ray Large Area Telescope Fourth Source Catalog Data Release 4 (4FGL-DR4) classifies 3935 gamma-ray sources as blazars. They are divided into two types, based on the equivalent width (EW): flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs). However, 1625 sources lack optical spectroscopic data and are tentatively classified as blazar candidates of uncertain type (BCUs). This work aims to spectroscopically classify a sample of BCUs, determine the redshifts, and estimate the masses of the central supermassive black holes (MBH) and the Doppler factors (delta) of the jets, in order to better understand their physical properties and provide valuable classifications for Cherenkov observatories. We cross-matched BCUs from the 4FGL-DR4 with the Sloan Digital Sky Survey Data Release 16 (SDSS-DR16) to obtain optical spectra. Sources were classified based on the EW of emission lines. For spectra with broad emission lines, MBH was estimated using the virial method. For absorption line dominated spectra, MBH was derived from the stellar velocity dispersion of the host galaxy. The delta was estimated for FSRQs using an empirical relation between their gamma-ray and broad-line region luminosities. We obtained and analyzed optical spectra for the candidate counterparts of 86 BCUs. Based on the spectral features, we confirmed 35 sources as FSRQs, 45 as BL Lacs, 3 as low-ionization narrow emission-line regions (LINERs), and 3 as regular elliptical galaxies, and we secured redshifts for 54 objects. We corrected the erroneous SDSS redshift for the counterparts of 4FGL J1047.9+0055 from 0.252 to 0.642. The black hole masses in log[MBH/M_{sun}_)]range from 7.07 to 9.22. The derived delta for 35 FSRQs spans from 3.62 to 35.43, with a mean value (delta) of 13.41. The distribution of our classified sources in the gamma-ray luminosity-photon index plane is consistent with that of the known blazars. Our spectroscopic analysis provides reliable classifications and key physical parameters for a large sample of BCUs. This work offers a crucial dataset for future statistical studies of blazars, their jet physics, and the connection between accretion processes and jet power.2026A&A...707A.347Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/707/A347CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toIX/67 : Incremental Fermi LAT 4th source cat. (4FGL-DR3) (Fermi-LAT col., 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/707/A347https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/707/A347http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/707/A347https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/707/A347https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/707/A347http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/707/A347GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/707/A347/table1 (Cross-matched results of BCU samples with SDSS spectra)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/707/A347/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/707/A347/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/707/A347/table1?GETtext/xml+votable180.050000true3.5864-5.0120.0055555555555555566/642 686 2094 2098 2568 4267 4862 5034 5166 5361 5781 5808 5952 6027 6044 6065 6211 6497 6582 7207 7553 8267 8514 8565 8585 8675 8717 8792 9016 9085 9338 9376 9524 9764 9835 10025 10120 10149 10535 10540 10553 10581 10740 10809 10814 10944 11136 11185 11260 11303 11418 17265 17366 17522 17642 17868 17882 17988 18240 18431 18954 19005 19209 19236 19465 19643 19839 19857 19870 19916 20074 20210 20419 27047 27257 27283 27525 27710 27763 27830 27998 28399 28615 28660 31636 36777https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/707/A347?format=asciiOpticalRadiodefaultJ/A+A/707/A347/table1Cross-matched results of BCU samples with SDSS spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAllDisplay all data for this sourcemeta.ref.urlchar4FGL4FGL namemeta.id;meta.maincharCtpAssociated counterpart name of the Fermi sourcemeta.id.assoccharSDSSSDSS spectral identifier in Plate-MJD-FiberID formatmeta.idcharRAJ2000Right Ascension of Fermi 4FGL source centroid (J2000)degpos.eq.ra;meta.mainDEJ2000Declination of Fermi 4FGL source centroid (J2000)degpos.eq.dec;meta.mainRACdegRight Ascension of Fermi associated counterpart (J2000)degpos.eq.raDECdegDeclination of Fermi associated counterpart (J2000)degpos.eq.decRASdegRight Ascension of matched SDSS spectrum (J2000)degpos.eq.raDESdegDeclination of matched SDSS spectrum (J2000)degpos.eq.decSepFermiSDSSAngular separation between Fermi centroid and SDSS spectrumdegpos.angDistancefloatePosFermi95% positional error radius of Fermi 4FGL source centroiddegstat.error;phys.angSizefloatSepCtpSDSSAngular separation between associated counterpart and SDSS spectrum, arcsecondsarcsecpos.angDistancefloatProbAssocAssociation probability given in the 4FGL catalogstat.fit.goodnessfloatSpInteractive spectrum from SDSS-DR14meta.ref.urlcharJ/A+A/707/A347/table2Spectral line measurements of BCU samples with SDSS spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAllDisplay all data for this sourcemeta.ref.urlchar4FGL4FGL namemeta.id;meta.maincharSDSSSDSS spectral identifier in Plate-MJD-FiberID formatmeta.idcharSNRSignal-to-noise ratio of the spectrumstat.snrfloatzSDSS? Redshift in SDSSsrc.redshift;pos.heliocentricfloatnullableClassClassification based on optical spectra (1)meta.code.class;src.classcharlambdaObs? Observed wavelength of the emission or absorption line (Angstroems)0.1nmem.wlfloatnullableLineType[AE] Line type: E for emission lines, A for absorption linesmeta.codecharLineIDLine identification with rest-frame wavelength (2)meta.id;em.wl;spect.linecharzline? Redshift derived from the linesrc.redshiftfloatnullablee_zline? Uncertainty in z_linestat.errorfloatnullableEW? Equivalent width of the line (Angstroms)0.1nmspect.line.eqWidthfloatnullablee_EW? Uncertainty in EW0.1nmstat.error;spect.line.eqWidthfloatnullableJ/A+A/707/A347/table3Black hole mass estimates and derived parameters for BCU samplese_FluxLine flux error (10^-17erg/s/cm^2^)1e-20W.m**-2stat.error;phot.fluxfloatlogLlineLogarithmic line luminosity (erg/s)log(1e-07W)phys.luminosityfloate_logLlineLogarithmic line luminosity error (erg/s)log(1e-07W)stat.errorfloatlogMBH? Logarithmic black hole masslog(solMass)phys.massfloatnullablee_logMBH? Logarithmic black hole mass errorlog(solMass)stat.errorfloatnullablelogLBLR? Logarithmic broad-line region luminosity (erg/s)log(1e-07W)phys.luminosityfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAllDisplay all data for this sourcemeta.ref.urlchar4FGL4FGL namemeta.id;meta.maincharzSDSSRedshift in SDSSsrc.redshift;pos.heliocentricfloatLineIDEmission line used for black hole mass estimationinstr.setup;spect.linecharLcont? Continuum luminosity (erg/s) (1)1e-07Wphys.luminosityfloatnullablee_Lcont? Continuum luminosity error (erg/s) (1)1e-07Wstat.errorfloatnullableFWHMFull width at half maximum of the emission linekm/sspect.line.widthdoublee_FWHMFull width at half maximum of the emission line errorkm/sstat.error;phys.angSizefloatFluxLine flux (10^-17erg/s/cm^2^)1e-20W.m**-2phot.flux;spect.linefloate_logLBLR? Logarithmic broad-line region luminosity error (erg/s)log(1e-07W)stat.errorfloatnullablelogLgamma? Logarithmic gamma-ray luminosity, log L_gamma(0.1-100 GeV) (erg/s)log(1e-07W)phys.luminosity;em.gammafloatnullablee_logLgamma? Logarithmic gamma-ray luminosity error (erg/s)log(1e-07W)stat.errorfloatnullableDoppler? Doppler factor estimated in this workspect.dopplerParamfloatnullable