Arp 220: New Observational Insights into the Structure and Kinematics of
  the Nuclear Molecular Disks and Surrounding Gas
  ALMA cycle 3 observations of $^{12}$CO $ J = 3\rightarrow2$, $^{13}$CO $J =
4\rightarrow 3$, SiO J = $8 \rightarrow 7$, and HCN J = $ 5 \rightarrow 4$ are
presented. Significant extended emission is detected in $^{12}$CO J $ =
3\rightarrow2$ with a morphology that is indicative of m = 2 tidal features,
suggesting gas inflow. In addition, outflow for both nuclei are found in the
$^{12}$CO J $ = 3\rightarrow2$. Significant SiO absorption is detected in the
western nucleus. HCN that is morphologically distinct from CO is detected in
both nuclei. These observations are compared to non-LTE radiative transfer
models created using the Line Modeling Engine (LIME) for simple gas dynamics to
gain insight into how physical parameters, such as rotational velocity,
turbulent velocity, gas temperature, dust temperature, and gas mass can
reproduce the observed kinematic and spatial features. The eastern nucleus is
found to be best modeled with an inclusion of a temperature asymmetry from one
side of the disk to the other. It is also found that the western nucleus is
optically thick even in the less abundant species of $^{13}$CO, absorbing
significant amounts of continuum radiation.
