Constraints on quasar broad line regions from microlensing

Gravitational microlensing is a powerful tool allowing one to unveil the structure of quasars on sub-parsec scale, and in particular of the broad emission line region. This is possible owing to the analysis of the microlensing-induced broad line deformation (core/wings or red/blue) observed in some gravitationally lensed quasars. After a description of examples of strong profile deformations, different in low- and high-ionization lines, we present newly developed simulations of line profile changes for various models of the emission line region in presence of microlensing. We explain how these simulations, confronted to observations of microlensed quasars, strongly favors the Keplerian disk model for the low-ionization emission line region. We also discuss how microlensing helps to probe the structure of other unresolved components, such as the broad absorption line and the continuum scattering regions.