The kinematics of the nebular shells around low mass progenitors of PNe
  with low metallicity
  We analyze the internal kinematics of 26 Planetary Nebulae (PNe) with low
metallicity that appear to derive from progenitor stars of the lowest masses,
including the halo PN population. Based upon spatially-resolved, long-slit,
echelle spectroscopy drawn from the San Pedro M\'artir Kinematic Catalogue of
PNe (L\'opez et al. 2012), we characterize the kinematics of these PNe
measuring their global expansion velocities based upon the largest sample used
to date for this purpose. We find kinematics that follow the trends observed
and predicted in other studies, but also find that most of the PNe studied here
tend to have expansion velocities less than 20 km/s in all of the emission
lines considered. The low expansion velocities that we observe in this sample
of low metallicity planetary nebulae with low mass progenitors are most likely
a consequence of a weak central star wind driving the kinematics of the nebular
shell. This study complements previous results (Pereyra et al. 2013, and
references therein) that link the expansion velocities of the PN shells with
the characteristics of the central star.
