J/A+A/424/519ivo://CDS.VizieR/J/A+A/424/519doi:10.26093/cds/vizier.34240519CDSHawkins M.R.S.2012-11-13T12:42:59Z2005-08-23T18:46:23ZCDS support team

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

cds-question@unistra.frquasarsactive-galactic-nucleispectroscopyIn this paper we report the discovery of a new class of active galactic nucleus in which although the nucleus is viewed directly, no broad emission lines are present. The results are based on a survey for AGN in which a sample of about 800 quasars and emission line galaxies were monitored yearly for 25 years. Among the emission line galaxies was the expected population of Seyfert 2 galaxies with only narrow forbidden lines in emission, and no broad lines. However, from the long term monitoring programme it was clear that some 10% of these were strongly variable with strong continuum emission. It is argued that these objects can only be Seyfert 1 galaxies in which the nucleus is viewed directly, but in which broad emission lines are completely absent. We compare these observations with other cases from the literature where the broad line region is reported to be weak or variable, and investigate the possibility that the absence of the broad line component is due to reddening. We conclude that this does not account for the observations, and that in these AGN the broad line region is absent. We also tentatively identify more luminous quasars from our sample where the broad emission lines also appear to be absent. The consequences of this for AGN models are discussed, and a case is made that we are seeing AGN in a transition stage between the fuel supply from a surrounding star cluster being cut off, and the nucleus becoming dormant.2004A&A...424..519Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/424/519CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/424/519https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/424/519http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/424/519https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/424/519https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/424/519http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/424/519GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/424/519/table1 (Seyfert galaxy line widths)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/424/519/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/424/519/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/424/519/table1?GETtext/xml+votable180.050000true320.219739-44.40088410.0055555555555555565/11681 11684 6/46638-46639 46650-46651 46723 46729 46732-46733 46744https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/424/519?format=asciiOpticaldefaultJ/A+A/424/519/table1Seyfert galaxy line widthszRedshiftsrc.redshiftfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAB1950Right ascension (B1950)pos.eq.ra;meta.mainDEB1950Declination (B1950)pos.eq.dec;meta.mainAmpBAmplitude in the Bj band measured over the period from 1975 to 2002magsrc.var.amplitudefloatFWHM[OII]FWHM line width of the [O II]3727 linekm/sspect.line.widthintFWHM[NeIII]FWHM line width of the [Ne III]3869 linekm/sspect.line.widthintFWHMH{beta}FWHM line width of the H{beta}4861 linekm/sspect.line.widthintFWHM[OIII]4FWHM line width of the [OIII]4959 linekm/sspect.line.width;em.line.OIIIintFWHM[OIII]5FWHM line width of the [OIII]5007 linekm/sspect.line.width;em.line.OIIIintFWHMH{alpha}FWHM line width of the H{alpha}6563 linekm/sspect.line.widthintO/HLine strength ratio [OIII]5007/H{beta}spect.line.intensity;em.line.OIII;arith.ratiofloat_RA.icrsRight ascension (ICRS) (computed by VizieR, not part of the original data)pos.eq.ranullableindexed_DE.icrsDeclination (ICRS) (computed by VizieR, not part of the original data)pos.eq.decnullableindexed