Numerical modelling of Auriga's Wheel - a new ring galaxy
  We model the formation of Auriga's Wheel - a recently discovered collisional
ring galaxy. Auriga's Wheel has a number of interesting features including a
bridge of stars linking the neighbouring elliptical to the ring galaxy, and
evidence for components of expansion and rotation within the ring. Using
N-body/SPH modelling, we study collisions between an elliptical galaxy and a
late-type disk galaxy. A near direct collision, with a mildy inclined disk, is
found to reasonably reproduce the general system morphology ~50 Myr following
the collision. The collision must have a relatively low velocity (initially
~150 km s^{-1}) in order to form the observed bridge, and simultaneously match
the galaxies separation. Our best-match model suggests the total disk galaxy is
~5 times more massive than the elliptical. We find that the velocity of
expansion of the ring is sensitive to the mass of the elliptical, while
insensitive to the encounter velocity. We evolve our simulation beyond the
current epoch to study the future destiny of the galaxy pair. In our model, the
nucleus moves further away from the plane of the ring in the direction of the
stellar bridge. The nucleus eventually merges with the elliptical galaxy ~100
Myr after the present time. The ring continues to expand for ~200 Myr before
collapsing back. The low initial relative velocity of the two galaxies will
eventually result in a complete merger.
