The Study On Galaxy Structure With Gravitational Lensing

Gravitational lensing is one of the consequences of Einstein's General Theory of Rel-ativity, and has been widely used in astrophysical research. We investigate the gravita-tional microlensing of quasars by stars and stellar remnants in the Milky Way, and givean estimate of the time-scale, event rate and optical depth using Monte Carlo simulations.Surveys such as Pan-STARRS and LSST should be able to detect about ten events per year,with typical event durations of around one month. Quasars are a kind of point sources atcosmological distances. Since microlensing of quasar sources sufers from fewer degen-eracies than lensing of Milky Way sources due to their large distances, they could be usedas a powerful tool for recovering the mass of the lensing object in a robust, often model-independent, manner. This method does not need the lensing object within a binary system.We predict that there will be one star can be given the mass by the quasar microlensingwith accurate astrometry from Gaia.For the moderate galaxy lensing, a new kind of gravitational lensing between strongand weak lensing, the magnification is of the order of～50%and no multiple imagesoccur as in strong galaxy lensing. We investigate the moderate lensing of backgroundelliptical galaxies by the intervening galaxies, and give an estimate of the optical depth asa function of redshift. Based on the design requirements of LSST, we obtain the lensedimages of the background elliptical galaxies, and present quantitatively the distortions onthe lensed images with the IRAF task ELLIPSE. We also present the fundamental planeof the lensed elliptical galaxies, and attribute the ofsets of the fundamental plane to themagnifications of the efective radii, while the mean surface brightnesses within the radiiare nearly the same as no lensing. By an inverse fitting process of the lensed images, weobtain the parameters of the de Vaucouleurs profile and the angular Einstein radius for aSIS lens model. If we can detect the redshifts of the lens and source galaxies, we canderive the velocity dispersion through the fitted angular Einstein radius, and the mass ofthe lens galaxy.