J/ApJ/794/75ivo://CDS.VizieR/J/ApJ/794/75doi:10.26093/cds/vizier.17940075CDSStevans M.L.Shull J.M.Danforth C.W.Tilton E.M.2017-07-03T13:37:16Z2017-05-12T16:15:25ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleigalaxiesspectroscopyultraviolet-photometryredshiftedhst-photometryvisible-astronomynarrow-band-photometryThe ionizing fluxes from quasars and other active galactic nuclei (AGNs) are critical for interpreting their emission-line spectra and for photoionizing and heating the intergalactic medium. Using far-ultraviolet (FUV) spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), we directly measure the rest-frame ionizing continua and emission lines for 159 AGNs at redshifts 0.001<z_AGN_<1.476 and construct a composite spectrum from 475 to 1875 {AA}. We identify the underlying AGN continuum and strong extreme ultraviolet (EUV) emission lines from ions of oxygen, neon, and nitrogen after masking out absorption lines from the H I Ly{alpha} forest, 7 Lyman-limit systems (N_HI_>=10^17.2^/cm2) and 214 partial Lyman-limit systems (14.5<logN_HI_<17.2). The 159 AGNs exhibit a wide range of FUV/EUV spectral shapes, F_v_{propto}{nu}^{alpha}_{nu}_^, typically with -2<={alpha}_{nu}_<=0 and no discernible continuum edges at 912 {AA} (H I) or 504 {AA} (He I). The composite rest-frame continuum shows a gradual break at {lambda}_br_{approx} 1000 {AA}, with mean spectral index {alpha}_{nu}_=-0.83+/-0.09 in the FUV (1200-2000 {AA}) steepening to {alpha}_{nu}_=-1.41+/-0.15 in the EUV (500-1000 {AA}). We discuss the implications of the UV flux turnovers and lack of continuum edges for the structure of accretion disks, AGN mass inflow rates, and luminosities relative to Eddington values.2014ApJ...794...75Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/794/75CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/ApJ/817/111 : HST/COS survey of z<0.9 AGNs. I. (Danforth+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/794/75https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/794/75http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/794/75https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/794/75https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/794/75http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/794/75GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/794/75/table1 (COS Observations (159 AGN Targets Ordered by Redshift))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/794/75/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/794/75/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/794/75/table1?GETtext/xml+votable180.050000true186.453833333.546750.0055555555555555566/0 2621 2663 2754 4204 4256 4821 4824 4961 4966 5215 5244 5262 5274 5409 5413 5437 5481 5529 5687 5731 5759 5773 5820 5821 5861 5974 6021 6081 6087 6104 6223 6488 6557 6606 7277 7381 7460 7508 7642 7998 8071 8282 8838 8867 8922 8939 8952 9018 9031 9175 9186 9440 9457 9753 9756 9783 9817 10162 10300 10433 10517 10602 10634 10659 10764 10889 10927 10940 10969 11014 11021 11209 11217 11388 11396 11490 11668 11898 12380 13414 15351 17075 17251 17488 17499 17673 17703 17730 17772 17990 18601 18770 19283 19700 19883 20008 22659 23060 23203 25742 25932 26017 26259 26270 26396 26859 26965 27006 27023 27079 27229 27250 27338 27350 27376 27526 27562 27720 28143 28201 28356 28395 28401 28468 28471 28527 28535 28546 28589 28636 31422 31658 32948 32986 32998 33126 33233 33796 33930 33950 34065 35180 35205 35741 35743 36443 36775 36788 37385 38268 38916 46281 46647 490421.5280350875291627e-18 1.8058597241943466e-18https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/794/75?format=asciiUVOpticaldefaultJ/ApJ/794/75/table1COS Observations (159 AGN Targets Ordered by Redshift)SimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintLyaindicates Lyman-limti systems in table 2meta.ref.urlcharAGNAGN target's namemeta.id;meta.maincharprimaryTypeAGN typesrc.classcharzRedshiftsrc.redshiftdoublealphalFitted spectral index (1)spect.indexfloate_alphalError in alphalstat.errorfloatF0Rest-frame flux normalization at 1100{AA} (in 10-14 erg/cm^2^/s/{AA})1e-16W.m**-2.nm**-1phot.flux;arith.ratiofloatFlObserved flux at 1300{AA} (in 10-14 erg/cm^2^/s/{AA}) (2)1e-16W.m**-2.nm**-1phot.fluxfloatloglLlBand luminosity at 1100{AA} (in erg/s)log(1e-07W)phys.luminosityfloatS/N1Signal-to-noise ratio at 1250{AA} and 1550{AA} for data with G130M (1132-1460{AA}) gratingstat.snrintS/N2Signal-to-noise ratio at 1250{AA} and 1550{AA} for data with G160M (1394-1798{AA}) gratingstat.snrint_RApositions from Simbad (right ascension part)degpos.eq.ra;meta.main_DEpositions from Simbad (declination part)degpos.eq.dec;meta.mainJ/ApJ/794/75/table2Lyman-limit Systems and Partial Lyman-limit SystemsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintAGNAGN target's namemeta.id;meta.maincharzRedshiftsrc.redshiftdoublelogNHILog of H I column densitylog(cm**-2)phys.columnDensityfloate_logNHIError in logNHIlog(cm**-2)stat.errorfloatbDoppler parameter (1)km/sspect.dopplerParamint