J/ApJS/257/30ivo://CDS.VizieR/J/ApJS/257/30doi:10.26093/cds/vizier.22570030CDSMooney S.Massaro F.Quinn J.Capetti A.Baldi R.D.Gurkan G.,Hardcastle M.J.Horellou C.Mingo B.Morganti R.O'Sullivan S.,Pajdosz-Smierciak U.Pandey-Pommier M.Rottgering H.2023-08-16T16:11:38Z2022-03-31T15:08:05ZCDS support team

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

cds-question@unistra.frbl-lacertae-objectsradio-sourcesgalaxy-classification-systemsredshiftedsurveysgamma-ray-astronomyWe present a morphological and spectral study of a sample of 99 BL Lac objects using the LOFAR Two-Metre Sky Survey Second Data Release (LDR2). Extended emission has been identified at gigahertz frequencies around BL Lac objects, but with LDR2 it is now possible to systematically study their morphologies at 144MHz, where more diffuse emission is expected. LDR2 reveals the presence of extended radio structures around 66/99 of the BL Lac nuclei, with angular extents ranging up to 115", corresponding to spatial extents of 410kpc. The extended emission is likely to be both unbeamed diffuse emission and beamed emission associated with relativistic bulk motion in jets. The spatial extents and luminosities of the extended emission are consistent with the unification scheme for active galactic nuclei, where BL Lac objects correspond to low-excitation radio galaxies with the jet axis aligned along the line of sight. While extended emission is detected around the majority of BL Lac objects, the median 144-1400MHz spectral index and core dominance at 144MHz indicate that the core component contributes ~42% on average to the total low-frequency flux density. A stronger correlation was found between the 144MHz core flux density and the {gamma}-ray photon flux (r=0.69) than between the 144MHz extended flux density and the {gamma}-ray photon flux (r=0.42). This suggests that the radio-to-{gamma}-ray connection weakens at low radio frequencies because the population of particles that give rise to the {gamma}-ray flux are distinct from the electrons producing the diffuse synchrotron emission associated with spatially extended features.2021ApJS..257...30Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/257/30CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)VII/274 : The Roma BZCAT - 5th edition (Massaro+, 2015)J/MNRAS/323/757 : Deep X-Ray Radio Blazar Survey (DXRBS). II. (Landt+, 2001)J/ApJS/171/61 : All-Sky Survey of Flat-Spectrum Radio Sources (Healey+, 2007)J/ApJ/741/30 : Radio/{gamma}-ray correlation in AGN (Ackermann+, 2011)J/ApJ/740/98 : Synchroton peak for blazars & radio galaxies (Meyer+, 2011)J/MNRAS/421/1569 : Properties of 18286 SDSS radio galaxies (Best+, 2012)J/ApJS/207/4 : Unidentified {gamma}-ray sources. III. Radio (Massaro+, 2013)J/ApJS/213/3 : Low-frequency flat spectrum sources (LORCAT) (Massaro+, 2014)J/A+A/588/A141 : The MWA view of Fermi blazars (Giroletti+, 2016)J/A+A/598/A104 : LOFAR Two-metre Sky Survey (Shimwell+, 2017)J/MNRAS/474/5008 : Radio spectral index 147-1400MHz (de Gasperin+, 2018)J/A+A/622/A1 : LOFAR Two-metre Sky Survey DR1 source cat. (Shimwell+, 2019)J/ApJS/247/33 : The Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)J/ApJ/892/105 : 4th catalog of Fermi LAT-detected AGNs (4LAC) (Ajello+, 2020)J/ApJ/900/L34 : BL Lac objects and radio galaxies comparison (Massaro+, 2020)J/ApJS/247/71 : Large-scale environment of radio gal. II. (Massaro+, 2020)J/A+A/648/A104 : LOFAR LBA Sky Survey. I. (de Gasperin+, 2021)J/A+A/659/A1 : LOFAR Two-metre Sky Survey (LoTSS) DR2 (Shimwell+, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/257/30https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/257/30http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/257/30https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/257/30https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/257/30http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/257/30GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/257/30/table5 (Details of the Roma-BZCAT BL Lac (BZB) sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/257/30/table5?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/257/30/table5?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/257/30/table5?GETtext/xml+votable180.050000true11.98008339.8160.0055555555555555566/716 2140 2273 2340 2621 4861 4863 5049 5072 5107 5370 5412 5423 5432 5516 5556 5657 5698 5723 5769 5778 5836 5844 6018 6044 6088 6096 6242 6246 6464 6487 6504 6629 7180 7190 7233 7238 7246 7285 7410 7433 7518 9202 9612 9637 9773 9811 9849 9872 9984-9985 10154 10220 10389 10409 10510 10514 10572 10605 10669 10715 10748-10749 10798 10805 10810 10825 10836 10843 10896 10912 10938 11100 11143 11178 11223 11242 11253 11268 11430 11449 11585 11598 11682 11795 11798 11838 11876 11925 11936 13324 19831 20136 20456 28115 28664 327299.54153977050123e-26 9.54153977050123e-26https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/257/30?format=asciiGamma-rayOpticalRadiodefaultJ/ApJS/257/30/table5Details of the Roma-BZCAT BL Lac (BZB) sampleNameName (JHHMM+DDMM)meta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint5BZBBZCAT v5 (Cat. VII/274) name (JHHMM+DDMM; <[MML2015] 5BZB JHHMM+DDMMa> in Simbad)meta.id.crosscharRAJ2000[11.98/356] Right Ascension (J2000)degpos.eq.ra;meta.mainDEJ2000[18.6/67.7] Declination (J2000)degpos.eq.dec;meta.mainzspec[0.03/0.761] Spectroscopic Redshiftsrc.redshiftdoubleClassClass, resolved ("rBZB": 66 occurrences) or "uBZB"=unresolved BZBsrc.classcharMorphMorphology ("Beamed", "Compact" or "Diffuse")src.morphcharStot[0.8/2162] Integrated flux density at 144MHz from LDR2mJyphot.flux.density;em.radio.100-200MHzfloatSimbadNameSimbad column added by the CDSmeta.idcharnullable4FGL4FGL name (JHHMM.m+DDMM)meta.id.crosscharResFlag indicating source resolved ("TRUE")meta.code.errorchare_Stot[0.16/433] Uncertainty in StotmJystat.errorfloatSGeV[7.6e-11/3.8e-8]? {gamma}-ray flux from 4LACph.cm**-2.s**-1phot.flux.density;em.gamma.harddoublenullablee_SGeV[2.3e-11/3.6e-10]? Uncertainty in SGeVph.cm**-2.s**-1stat.errordoublenullablealpha[-1.26/1.95] Spectral index, 144-1400MHz with LDR2 and NVSSspect.index;em.radio.750-1500MHzfloate_alpha[0.002/0.4] Uncertainty in alphastat.error;pos.eq.rafloatrho144[0.02/2.97]? Core dominance at 144MHz (see Section 3.2)phot.flux;arith.ratiodoublenullablee_rho144[0.004/0.6]? Uncertainty in rho144stat.errordoublenullableLimitFlag indicating spatial/angular extents are upper limits ("TRUE")meta.codecharD[3.7/411] Spatial extentkpcphys.size.diameterdoublee_D[0.002/136] Uncertainty in Dkpcstat.errordoublephi[2.68/116] Angular extentarcsecphys.angSizedoublee_phi[0.002/21] Uncertainty in phiarcsecstat.errorfloatL144[5.8e+23/6.5e+26] Radio luminosityW/Hzphys.luminosity;em.radio.100-200MHzdoublee_L144[1.1e+23/1.3e+26] L144 uncertaintyW/Hzstat.errordoubleLoTSSLoTSS DR2 name (ILTJHHMMSS.ss+DDMMSS.s)meta.id;meta.mainchar