On the geometry of broad emission region in quasars |
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| Authors: | R Decarli M Labita A Treves R Falomo |
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| Institution: | Universitàdegli Studi dell'Insubria, via Valleggio 11, 22100 Como, Italy;INAF –Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy |
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| Abstract: | We study the geometry of the Hβ broad emission region by comparing the M BH values derived from Hβ through the virial relation with those obtained from the host galaxy luminosity in a sample of 36 low-redshift ( z ∼ 0.3) quasars. This comparison lets us infer the geometrical factor f needed to deproject the line-of-sight velocity component of the emitting gas. The wide range of f values we found, together with the strong dependence of f on the observed linewidth, suggests that a disc-like model for the broad-line region is preferable to an isotropic model, both for radio-loud and radio-quiet quasars. We examined similar observations of the C iv line and found no correlation in the width of the two lines. Our results indicate that an inflated disc broad-line region, in which the Carbon line is emitted in a flat disc while Hβ is produced in a geometrically thick region, can account for the observed differences in the width and shape of the two emission lines. |
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| Keywords: | galaxies: active galaxies: nuclei quasars: emission lines quasars: general |
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