Applications of gravitational lensing: Revealing the structure of quasars
Abstract:
There is no chance of spatially resolving the inner parts of active galactic nuclei (AGNs) with current optical telescopes, therefore observations of gravitationally lensed quasars and galaxies provide a powerful alternative to study their inner parts and distribution of mass. Compact objects such as stars in the lens galaxy induce uncorrelated changes in the flux of the images. This microlensing effect can help us overcoming these difficulties as it is sensitive to the size of the emitting region and thus, can be used to extract information about both the source and the lens. Photometric monitoring and spectroscopic observations in different epochs are a powerful technique to measure the dimensions of the different emitting regions in a gravitationally lensed quasar and to probe their kinematics. In this talk I will show how to use gravitational microlensing to reveal the size and geometry of AGNs on different scales, starting from the broad-line region (BLR), followed by the accretion disk, down to the smallest region of the AGN—the central supermassive black hole (SMBH).