Two-component mass models of the lensing galaxy in the quadruply imaged
  supernova iPTF16geu
  The first resolved, multiply imaged supernova Type Ia, iPTF16geu, was
observed 4 years ago, five decades after such systems were first envisioned.
Because of the unique properties of the source, these systems hold a lot of
promise for the study of galaxy structure and cosmological parameters. However,
this very first example presented modelers with a few puzzles. It was expected
that to explain image fluxes a contribution from microlensing by stars would be
required, but to accommodate the magnitude of microlensing, the density slope
of the elliptical power law lens model had to be quite shallow, $\rho_{2D}
\propto r^{-0.7}$. Furthermore, the center of mass had to be displaced from
that of observed light by ~0.1 kpc, and the position angle of light
distribution was misaligned with that of mass by ~40 degrees. In this paper we
present mass models that resolve the first two problems, and suggest a
resolution of the third. Motivated by observations of local ellipticals, and
some recent analysis of galaxy-scale lenses, our mass models consist of two
offset (baryonic) mass components. The resulting mass distributions have a
single centroid, but are lopsided, and have isodensity contours that are not
purely elliptical and not self-similar with radius. For many of our models the
microlensing requirements are modest, and the ring formed by the extended
supernova host galaxy resembles the observed one.
