White Dwarf Kinematics vs Mass
  We have investigated the relationship between the kinematics and mass of
young (<3x10^8 years) white dwarfs using proper motions. Our sample is taken
from the colour selected catalogues of SDSS (Eisenstein et al. 2006) and the
Palomar-Green Survey (Liebert, Bergeron & Holberg 2005), both of which have
spectroscopic temperature and gravity determinations. We find that the
dispersion decreases with increasing white dwarf mass. This can be explained as
a result of less scattering by objects in the Galactic disk during the shorter
lifetime of their more massive progenitors. A direct result of this is that
white dwarfs with high mass have a reduced scale height, and hence their local
density is enhanced over their less massive counterparts. In addition, we have
investigated whether the kinematics of the highest mass white dwarfs
(>0.95Msun) are consistent with the expected relative contributions of single
star evolution and mergers. We find that the kinematics are consistent with the
majority of high-mass white dwarfs being formed through single star evolution.
