  Sixteen RR Lyrae variables from the QUEST survey that lie in the leading arm
of the tidal stream from the Sagittarius dSph galaxy have been observed
spectroscopically to measure their radial velocities and metal abundances. The
systemic velocities of 14 stars, which were determined by fitting a standard
velocity curve to the individual measurements, have a sharply peaked
distribution with a mean of 33 km/s and a standard deviation of only 25 km/s.
The [Fe/H] distribution of these stars has a mean of -1.76 and a standard
deviation of 0.22. These measurements are in good agreement with previous ones
from smaller samples of stars. The mean metallicity is consistent with the
age-metallicity relation that is observed in the main body of the Sgr dSph
galaxy.
  The radial velocities and the distances from the Sun of these stars are
compared with recent numerical simulations of the Sgr streams that assume
different shapes for the dark matter halo. Models that assume a oblate halo do
not fit the data as well as ones that assume a spherical or a prolate
distribution. However, none of the fits are completely satisfactory. Every
model fails to reproduce the long extent of the stream in right ascension (36
degr) that is seen in the region covered by the QUEST survey. Further modeling
is required to see if this and the other mismatches between theory and
observation can be removed by judicial choices for the model parameters or
instead rule out a class of models.
