An accurate analytic mass model for lensing galaxies
  We develop an analytic mass model for lensing galaxies, based on a broken
power-law (BPL) density profile, which is a power-law profile with a mass
deficit or surplus in the central region. Under the assumption of an
elliptically symmetric surface mass distribution, the deflection angle and
magnification can be evaluated analytically for this new model. We compute the
theoretical prediction for various quantities, including the volume and surface
mass density profiles of the galaxies, and the aperture and luminosity-weighted
line-of-sight velocity dispersions, and compare them to those measured from the
Illustris simulation. We find an excellent agreement between our model
prediction and the simulation, which validates our modeling. The high
efficiency and accuracy of our model manifests itself as a promising tool for
studying properties of galaxies with strong lensing.
