The Complex Structure of Stars in the Outer Galactic Disk as revealed by
  Pan-STARRS1
  We present a panoptic view of the stellar structure in the Galactic disk's
outer reaches commonly known as the Monoceros Ring, based on data from
Pan-STARRS1. These observations clearly show the large extent of the stellar
overdensities on both sides of the Galactic disk, extending between b = -25 and
b = +35 degrees and covering over 130 degrees in Galactic longitude. The
structure exhibits a complex morphology with both stream-like features and a
sharp edge to the structure in both the north and the south. We compare this
map to mock observations of two published simulations aimed at explaining such
structures in the outer stellar disk, one postulating an origin as a tidal
stream and the other demonstrating a scenario where the disk is strongly
distorted by the accretion of a satellite. These morphological comparisons of
simulations can link formation scenarios to observed structures, such as
demonstrating that the distorted-disk model can produce thin density features
resembling tidal streams. Although neither model produces perfect agreement
with the observations--the tidal stream predicts material at larger distances
which is not detected while in the distorted disk model the midplane is warped
to an excessive degree--future tuning of the models to accommodate these latest
data may yield better agreement.
