Researches On The Broad Line Regions In Active Galaxies Nuclei

In this PhD thesis, we study the origin and the geometry of broad emission line regions of Active Galactic Nuclei(AGN).Most bright active galactic nuclei (AGNs) exhibit broad emission lines, of which the full width at half maximum (FWHM) are ≥ 10³ kms^-1 ([96]). Some type 1 AGNs could have very broad emission lines (FWHM≥ 20,000 kms^-1). Type 2 AGNs show only narrow lines (FWHM≤1000 km s^-1) and at least some of them show evidence of containing hidden type 1 AGNs ([6, 121, 126, 127])。 The origin of BLRs is still unclear. One scenario is that the BLRs originate from the winds accelerated from the hot coronae of the disks ([87]), and the winds are suppressed when the black holes are accreting at low rates.This model predicts a relation between m|· (m|· = M|·/M|·_Edd) and the FWHM of broad emission lines. We estimate the central black hole masses for a sample of bright AGNs by using their broad H_β line-widths and optical luminosities. The dimensionless accretion rates m|· = M|·/M|·_Edd are derived from the optical continuum luminosities by using two different models: 1.using an empirical relation between the bolometric luminosity L_bol and the optical luminosity, ( m|· = L_bol/L_Edd, a fixed radiative efficiency is adopted); 2.calculating the optical spectra of accretion disks as the function of m|·. We find a significant correlation between the derived m|· and the observed line width of H_β, FWHM ∝ m|·^-0.37, which almost overlaps the disk-corona model calculations, if the viscosity α ≈ 0.1—0.2 is adopted. Our results provide strong evidence for the physical link between the BLRs and accretion disks in AGNs。The geometry of broad-line regions in active galactic nuclei (AGNs) is still controversial.The BLR sizes of broad-line Hβ are measured by Kaspi et al. (2000) for a sample of quasars and Seyfert galaxies using reverberation mapping method. They found a tight correlation between the BLR size and optical continuum luminosity \L\. In the unification scheme, the jets of BL Lac objects are supposed to be inclined at small angles with respect to the line of sight (see Urry & Padovani, 1995 for a review), so the broad-line profiles will be significantly narrowed if disk-...