The Gini Coefficient as a Morphological Measurement of Strongly Lensed
  Galaxies in the Image Plane
  Characterization of the morphology of strongly lensed galaxies is challenging
because images of such galaxies are typically highly distorted. Lens modeling
and source plane reconstruction is one approach that can provide reasonably
undistorted images from which morphological measurements can be made, although
at the expense of a highly spatially variable telescope PSF when mapped back to
the source plane. Unfortunately, modeling the lensing mass is a time and
resource intensive process, and in many cases there are too few constraints to
precisely model the lensing mass. If, however, useful morphological
measurements could be made in the image plane rather than the source plane, it
would bypass this issue and obviate the need for a source reconstruction
process for some applications. We examine the use of the Gini coefficient as
one such measurement. Because it depends on the cumulative distribution of the
light of a galaxy, but not the relative spatial positions, the fact that
surface brightness is conserved by lensing means that the Gini coefficient may
be well-preserved by strong gravitational lensing. Through simulations, we test
the extent to which the Gini coefficient is conserved, including by effects due
to PSF convolution and pixelization, to determine whether it is invariant
enough under lensing to be used as a measurement of galaxy morphology that can
be made in the image plane.
