文档介绍：Estimating the black hole masses of AGNs from emission line properties
Ran Wang
Department of Astronomy, Peking University
Abstract
Empirical relations between the BLR size and continuum luminosity have been derived and widely used to calculate the BLR sizes and black hole masses of large samples of AGNs. However, optical and ultraviolet continuum may be affected significantly by jets for radio-loud AGNs. To avoid this affection, we first use the emission line luminosity instead of the continuum luminosity as the representative of ionizing luminosity. In the optical band, we find a reliable empirical relation between the BLR size and Hβ line luminosity,, with a sample of 34 AGNs. Furthermore when applying this relation to calculate the black hole mass of radio-loud AGNs, we get lower black hole pared to the values estimated with the R-L5100Å relation. Such a difference es more obvious when the radio-loudness increases, consistent with our prediction. In the ultraviolet band, we find another tight empirical relation between the BLR size and Mg II emission line luminosity, , from 26 AGNs in the sample above with the ultraviolet spectra available. Then the two relations are applied to estimate the black hole masses of a sample of 80 AGNs in the Large Bright Quasar Survey. The black hole masses estimated from these two estimations have a best-fitting relation with a slope of , which indicates that the estimation with Mg II emission line luminosity is reliable. Therefore, we conclude that the emission line luminosity is more suitable than the continuum luminosity to be used to derive the BLR size of AGNs, and the estimation of black hole mass from the emission line luminosity is more accurate.
The idea that the active galactic nuclei (AGN) has a supermassive black hole in its centre is widely realized and accepted. So how to accurately estimate the central black hole mass correctly es more and more important. With a fundamental assumption t