Gravitational microlensing of quasar broad-line regions at large optical depths

Abstract

Recent estimates of the scale of structures at the heart of quasars suggest that the regions responsible for the broad-line emission are smaller than previously thought. With this revision of scale, the broad-line region is amenable to the influence of gravitational microlensing. This study investigates the influence on microlensing at high optical depth on a number of current models of the broad-line region (BLR). It is found that the BLR can be significantly magnified by the action of microlensing, although the degree of magnification is dependent upon the spatial and kinematic structure of the BLR. Furthermore, while there is a correlation between the microlensing fluctuations of the continuum source and the BLR, there is substantial scatter about this relation, revealing that broad-band photometric monitoring is not necessarily a guide to microlensing of the BLR. The results of this study demonstrate that the spatial and kinematic structure within the BLR may be determined via spectroscopic monitoring of microlensed quasars.