J/A+A/569/A95ivo://CDS.VizieR/J/A+A/569/A95doi:10.26093/cds/vizier.35690095CDSKuegler S.D.Nilsson K.Heidt J.Esser J.Schultz T.2018-01-04T08:22:24Z2014-12-17T12:02:15ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleibl-lacertae-objectspolarimetryDeep optical surveys open the avenue for finding large numbers of BL Lac objects that are hard to identify because they lack the unique properties classifying them as such. While radio or X-ray surveys typically reveal dozens of sources, recent compilations based on optical criteria alone have increased the number of BL Lac candidates considerably. However, these compilations are subject to biases and may contain a substantial number of contaminating sources. In this paper we extend our analysis of 182 optically selected BL Lac object candidates from the SDSS with respect to an earlier study. The main goal is to determine the number of bona fide BL Lac objects in this sample. We examine their variability characteristics, determine their broad-band radio-UV spectral energy distributions (SEDs), and search for the presence of a host galaxy. In addition we present new optical spectra for 27 targets with improved signal-to-noise ratio with respect to the SDSS spectra. At least 59% of our targets have shown variability between SDSS DR2 and our observations by more than 0.1-0.27mag depending on the telescope used. A host galaxy was detected in 36% of our targets. The host galaxy type and luminosities are consistent with earlier studies of BL Lac host galaxies. Simple fits to broad-band SEDs for 104 targets of our sample derived synchrotron peak frequencies between 13.5<=log_10_({nu}_peak_)<=16 with a peak at log_10_~14.5. Our new optical spectra do not reveal any new redshift for any of our objects. Thus the sample contains a large number of bona fide BL Lac objects and seems to contain a substantial fraction of intermediate-frequency peaked BL Lacs.2014A&A...569A..95Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/569/A95CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/AJ/129/2542 : BL Lac from SDSS (Collinge+, 2005)J/A+A/529/A162 : Optically selected BL Lac cand. polarimetry (Heidt+, 2011)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/569/A95https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/569/A95http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/569/A95https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/569/A95https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/569/A95http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/569/A95GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/569/A95/tablea2 (Main properties objects discussed in Heidt & Nilsson (2011, J/A+A/529/A162) and the present work)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/569/A95/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/569/A95/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/569/A95/tablea2?GETtext/xml+votable180.050000true0.3394583-0.19452780.0055555555555555566/1 4096 4098 4108 5960 6103 6110 6132 6255 6404 6464 6540 6554 7257 7262 7269 7285 7302 7380 7433 7448 7475 7478 7490 7507 7530 7569 8195 8203 9472 9600 9618 9637 9823 9855 9950 10105 10154 10202 10219 10994 11004 11143 11168 11176 11223 11242 11253 11260 11385 11444 11456 11460 11467 11585 11798 11832 11838 11912 11915 12546 12548 17239 17264 17516 17553 17579 17602 17745 17749 17754-17756 17817 17820 17835 17997 18005 18020 18075 18090 18096 18402 18407 18604 18772 18837 18852-18854 19033-19034 19042 19110 19325 19756 19778 20034 21855 21879 22717 22927 23181 23208 25849 25855 25910 25954 26016 26036 26056 26067 26073-26074 26083 26087 26203 26228 26242 26247 26254 26256 26270 26276-26277 26305 26308 26310 26341 26406 26964 26983 26986 26998 27003 27032 27036 27056 27060 27063-27064 27082 27198 27217 27246-27247 27249 27251 27257 27311 27319 27321 27329 27405 27420 27428 27653 27669 27671 27675 31318 31354 31424 32511 36728 36779 36784 36801 49010 49019 49124 491512.85864675833786e-19 3.5010283109654867e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/569/A95?format=asciiOpticaldefaultJ/A+A/569/A95/table3Host galaxy results for the bulge modelrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSTarget SDSS designation (HHMMSS.ss+DDMMSS.s)meta.id;meta.maincharTelTelescope used: CA=Calar Alto 2.2m, NOT=Nordic Optical Telescope, NTT at ESOinstr.setupcharz[0.04/0.71]? Redshift, listed only when the redshift determination is securesrc.redshiftfloatnullablermag.c? SDSS r' magnitude of the core m_c_magphot.mag;em.opt.Rfloatnullablee_rmag.c? rms uncertainty in rmag.cmagstat.errorfloatnullablermag.gr' magnitude of the host galaxy m_g_magphot.mag;em.opt.Rfloate_rmag.grms uncertainty in rmag.gmagstat.errorfloatre[0.5/8.4] Effective radius r_e_arcsecphys.angSizefloate_rerms uncertainty on rearcsecstat.errorfloatell.g[0/1] Ellipticity of host galaxy {epsilon}_g_src.ellipticityfloatpa.gPosition angle of the host galaxy {theta}_g_degpos.posAngintT.g[BU] Host galaxy type: B=bulge, U=undefinedsrc.classcharfc[0/1] Fraction of the core flux in total fluxphot.flux;arith.ratiofloate_fcrms uncertainty on fcstat.errorfloatu_fc[)] Uncertainty flag on fcmeta.code.errorcharrMAG? Absolute r' magnitude M_r'_magphys.magAbsfloatnullableRe? Effective radius in kpckpcphys.size.radiusfloatnullableJ/A+A/569/A95/tablea2Main properties objects discussed in Heidt & Nilsson (2011, J/A+A/529/A162) and the present workVampVariability amplitudemagsrc.var.amplitudefloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintPapISimbad column added by the CDSmeta.ref.urlcharSDSSTarget SDSS designation (HHMMSS.ss+DDMMSS.s)meta.id;meta.maincharprimaryMNumber of observations + bulge modeling for this galaxymeta.ref.urlintnullablel_zLimit flag on zmeta.code.error;src.redshiftcharz[0.04/5.1]? SDSS spectroscopic redshiftsrc.redshiftfloatnullableu_z[u] SDSS z flag (u for uncertain)meta.code.error;src.redshiftcharl_aoxLimit flag on aoxmeta.code.errorcharaoxSpectral index Optical/X-ray {alpha}_ox_ (1)spect.indexfloatl_aroLimit flag on arometa.code.errorchararo? Spectral index Radio/Optical {alpha}_ro_ (1)spect.indexfloatnullablel_PolLimit flag on Polmeta.code.errorcharPol? Polarisation%phys.polarizationfloatnullablee_Pol? rms uncertainty on Pol%stat.errorfloatnullableVL[0.03/0.15] Variability limitmagphot.magfloatf_Vamp[-] Variability amplitude is negative?meta.codecharl_fcLimit flag on fcmeta.code.errorcharfcCore (AGN) fraction over the total flux fraction as derived from the host galaxy fitsphot.flux;arith.ratiofloate_fc? rms uncertainty on fcstat.errorfloatnullablelognuP? Peak frequency determined from SED fitslog(Hz)stat.fit.paramfloatnullablef_lognuPFlag for uncertain lognuP with respect to the SED fits (2)meta.codecharSloanDisplay the SDSS data for this sourcemeta.ref.urlchar_RAPositions from SDSS name (right ascension part)degpos.eq.ra;meta.main_DEPositions from SDSS name (declination part)degpos.eq.dec;meta.main