Geometry of the Broad Line Region in AGN

Abstract

Values of black hole masses are frequently determined with the help of the reverberation method. This method is based on the measurements of widths of the broad emission lines as well as time delays between the lines and the continuum. The above method requires a specific assumption about the distribution of the orbits of the Broad Line Region (BLR) clouds. In the case of a spherical cloud distribution, the geometrical factor f2 = 0.75 [1] which corresponds to this geometry is adopted. [2] determined the value f2 ∼ 1.37 The determined value is based on the relation of the black hole mass to the velocity dispersion. In our calculations we have determined this factor by using an independent mass determination from the X‐ray variance method (based on X‐ray variability) for a number of Seyfert 1 galaxies. The value of f2 is equal to 1.12 ± 0.54. Both values are larger than 0.75 and show that the BLR is rather more flat than spherical.