Paper detail

On the observed distributions of black hole masses and Eddington ratios from radiation pressure corrected virial indicators

The application of the virial theorem to the Broad Line Region of Active Galactic Nuclei allows Black Hole mass estimates for large samples of objects at all redshifts. In a recent paper we showed that ionizing radiation pressure onto BLR clouds affects virial BH mass estimates and we provided empirically calibrated corrections. More recently, a new test of the importance of radiation forces has been proposed: the MBH-sigma relation has been used to estimate MBH for a sample of type-2 AGN and virial relations (with and without radiation pressure) for a sample of type-1 AGN extracted from the same parent population. The observed L/LEdd distribution based on virial BH masses is in good agreement with that based on MBH-sigma only if radiation pressure effects are negligible, otherwise significant discrepancies are observed. In this paper we investigate the effects of intrinsic dispersions associated to the virial relations providing MBH, and we show that they explain the discrepancies between the observed L/LEdd distributions of type-1 and type-2 AGN. These discrepancies in the L/LEdd distributions are present regardless of the general importance of radiation forces, which must be negligible only for a small fraction of sources with large L/LEdd. Average radiation pressure corrections should then be applied in virial MBH estimators until their dependence on observed source physical properties has been fully calibrated. Finally, the comparison between MBH and L/LEdd distributions derived from sigma-based and virial estimators can constrain the variance of BLR physical properties in AGN.