On the Origin of the Monoceros Ring - I: Kinematics, proper motions, and
  the nature of the progenitor
  The Monoceros Ring (MRi) structure is an apparent stellar overdensity that
has been postulated to entirely encircle the Galactic plane and has been
variously described as being due to line-of-sight effects of the Galactic warp
and flare or of extragalactic origin (via accretion). Despite being intensely
scrutinised in the literature for more than a decade, no studies to-date have
been able to definitively uncover its origins. Here we use $N$-body simulations
and a genetic algorithm to explore the parameter space for the initial
position, orbital parameters and, for the first time, the final location of a
satellite progenitor. We fit our models to the latest Pan-STARRS data to
determine whether an accretion scenario is capable of producing an in- Plane
ring-like structure matching the known parameters of the MRi. Our simulations
produce streams that closely match the location, proper motion and kinematics
of the MRi structure. However, we are not able to reproduce the mass estimates
from earlier studies based on Pan-STARRS data. Furthermore, in contrast with
earlier studies our best-fit models are those for progenitors on retrograde
orbits. If the MRi was produced by satellite accretion, we find that its
progenitor has an initial mass upper limit of ~$10^{10}$M$_\odot$ and the
remnant is likely located behind the Galactic bulge, making it diffcult to
locate observationally. While our models produce realistic MRi-like structures
we cannot definitively conclude that the MRi was produced by the accretion of a
satellite galaxy.
