Gravitational Microlens Mapping of a Quasar Accretion Disk

Since the radiation from different portions in the central region of a quasar can be successively amplified during a microlensing event, microlensing light curves provide fruitful information regarding the emissivity distribution of an accretion disk located at the quasar center. We present a basic methodology of how to map the emissivity distribution of the disk as a function of the radial distance from the center, Q(r), from ‘observed’ microlens light curves during a caustic crossing event. Our proposed method is based on the standard inversion technique, the so-called regularization method, and Abel's transformation of the one-dimensional luminosity profile integrated along the line parallel to the caustics. This technique will be used to map the disk structure in Q2237+0305, for which the HST and AXAF observations are scheduled. A reconstruction of the image on length scales of several to ten AUs is quite feasible for this source, as long as the measuring errors are within 0.02 mag and the observation time intervals are one week or less.