Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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.

10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn