J/ApJ/789/140ivo://CDS.VizieR/J/ApJ/789/140doi:10.26093/cds/vizier.17890140CDSLiu X.Shen Y.Bian F.Loeb A.Tremaine S.2023-12-19T09:24:40Z2017-03-17T15:45:09ZCDS support team

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

cds-question@unistra.frquasarsspectroscopynarrow-band-photometryatomic-spectroscopyredshiftedA small fraction of quasars have long been known to show bulk velocity offsets (of a few hundred to thousands of km/s) in the broad Balmer lines with respect to the systemic redshift of the host galaxy. Models to explain these offsets usually invoke broad-line region gas kinematics/asymmetry around single black holes (BHs), orbital motion of massive (~sub-parsec (sub-pc)) binary black holes (BBHs), or recoil BHs, but single-epoch spectra are unable to distinguish between these scenarios. The line-of-sight (LOS) radial velocity (RV) shifts from long-term spectroscopic monitoring can be used to test the BBH hypothesis. We have selected a sample of 399 quasars with kinematically offset broad H{beta} lines from the Sloan Digital Sky Survey (SDSS) Seventh Data Release quasar catalog, and have conducted second-epoch optical spectroscopy for 50 of them. Combined with the existing SDSS spectra, the new observations enable us to constrain the LOS RV shifts of broad H{beta} lines with a rest-frame baseline of a few years to nearly a decade. While previous work focused on objects with extreme velocity offset (>10^3^ km/s), we explore the parameter space with smaller (a few hundred km/s) yet significant offsets (99.7% confidence). Using cross-correlation analysis, we detect significant (99% confidence) radial accelerations in the broad H{beta} lines in 24 of the 50 objects, of ~10-200 km/s/yr with a median measurement uncertainty of ~10 km/s/yr, implying a high fraction of variability of the broad-line velocity on multi-year timescales. We suggest that 9 of the 24 detections are sub-pc BBH candidates, which show consistent velocity shifts independently measured from a second broad line (either H{alpha} or Mg II) without significant changes in the broad-line profiles. Combining the results on the general quasar population studied in Paper I (Shen et al. 2013ApJ...775...49S), we find a tentative anti-correlation between the velocity offset in the first-epoch spectrum and the average acceleration between two epochs, which could be explained by orbital phase modulation when the time separation between two epochs is a non-negligible fraction of the orbital period of the motion causing the line displacement. We discuss the implications of our results for the identification of sub-pc BBH candidates in offset-line quasars and for the constraints on their frequency and orbital parameters.2014ApJ...789..140Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/789/140CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)J/MNRAS/251/482 : A spectroscopic survey of faint QSOs (Boyle+ 1991)J/MNRAS/367/1261 : Redshift survey in 15 quasar fields (Morris+, 2006)J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)J/MNRAS/405/2302 : Improved redshifts for SDSS quasar spectra (Hewett+, 2010)J/ApJ/680/169 : SDSS DR5 virial black hole masses (Shen+, 2008)J/MNRAS/434/1411 : Variability of broad emission lines in QSOs (Woo+, 2013)J/ApJ/814/150 : Variability of SDSS broad absorption line QSOsJ/ApJ/831/7 : SDSS-RM project: peak velocities of QSOs (Shen+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/789/140https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/789/140http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/789/140https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/789/140https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/789/140http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/789/140GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/789/140/table1 (SDSS Quasars with kinematically offset broad balmer emission lines)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/789/140/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/789/140/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/789/140/table1?GETtext/xml+votable180.050000true3.1000983-10.37404190.0055555555555555566/0 526 904 2040 2199 4098 4111 4173 4194 4210 4234 4250 4261 4285 4306 4312 4337 4347 4410 4436 4444 4468 4502 4533 4542 4555 4574 4578 4601 4611 4617 4651 4695 4748 4759 4775 4781 4801-4803 4829 4845 4916 4929 4952 4961 4984 4989 5002-5003 5008 5025 5029 5065 5102 5111 5132 5216 5247 5265 5305 5312 5347 5354 5359 5372 5397 5483 5505 5540 5545 5550 5552 5562 5568 5586 5594 5667 5680 5718 5727 5749 5755 5767 5769 5774 5797 5803 5828 5839 5881 5893 5915 5948 5951 5973 5988 5993 6011 6062 6064 6072 6128 6223 6229 6264 6267 6269-6270 6340 6384 6437 6549 6555 6557 6562 6582 6618 6620 7223 7235 7256 7268 7280 7287 7305 7308 7310 7343 7365 7381 7435 7452 7477 7492 7495 7508 7523 7554 7562 7564 8227 8230 8258 8260 8279 8293 8340 8348 8390 8394 8432 8484 8519 8521-8522 8576 8630 8638 8645 8742 8750 8788 8841 8853 8876 8881 8988-8989 8993 9074 9101-9102 9116 9164 9191 9200 9208 9237 9284 9295 9351 9372 9381 9459 9466 9513 9519 9632 9728 9785 9805 9842 9891 9906 9919 9923 9939 10020 10026 10092 10217 10276 10428 10431 10450 10516 10520 10558 10585 10589 10597 10616 10631 10648 10757 10766 10872 10891 10918 10961 10965 10986 11004 11142 11146 11181 11193 11239 11290 11293 11295-11296 11339 11355 11395 11402 11469 11495 11502 11512 11530 11587 11787 11813 11854 11881 11883 11907 12547 17251 17260 17308 17471 17497 17551 17560 17574 17753 17771 17811 17840 17921 18027 18061 18063 18070 18093 18096 18171 18385 18515 18519 18545-18546 18617 18628 18687 18773 19006 19023 19028-19029 19105 19669 19736 19778 19992 20003 20158 22364 23193 23211 23216 26019 26074 26121 26172 26268 26294 26328 26337 26342 26363 26369 26376 26420 26453 26485 26488 26522 26527 26563 26955 27029 27033 27049 27077 27097 27101 27111 27124 27255 27290 27331 27338 27409 27435 27451 27467 27526 27578 27618 27628 27653 27656 27691 27715 27717 27738 27824 27828 27836 27864 27880 27936 27959 27982 27992 28025 28049 28068 28176 28210 28216 28222 28236 28293-28294 28317 28351 28354 28373 28381 28395 28419 28445 28448 28585 28593 28651 30038 30043 31333 31353 31375 31384 31405 31477 31482 31546 31661 31693 31731 31740-31741 36729 36763 48990 49013 49017https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/789/140?format=asciidefaultJ/ApJ/789/140/table1SDSS Quasars with kinematically offset broad balmer emission linesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS designationmeta.id;meta.maincharzRedshift (1)src.redshiftfloatPlateSpectroscopic plate numbermeta.id;instr.plateintFiberFiber identificationmeta.idintMJDModified Julian Datedtime.epochintVOFFPBroad H{beta} peak velocity offset (2)km/sspect.dopplerVelocinte_VOFFPThe 1{sigma} uncertainty in VOFFP (3)km/sstat.errorintVOFFCBroad H{beta} centroid velocity offsetkm/sspect.dopplerVelocintSpInteractive spectrum from SDSSmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.main