Palomar 5 and its Tidal Tails: A Search for New Members in the Tidal
  Stream
  In this paper we present the results of a search for members of the globular
cluster Palomar 5 and its associated tidal tails. The analysis has been
performed using intermediate and low resolution spectroscopy with the AAOmega
spectrograph on the Anglo-Australian Telescope. Based on kinematics, line
strength and photometric information, we identify 39 new red giant branch stars
along $\sim$20$^{\circ}$ of the tails, a larger angular extent than has been
previously studied. We also recover eight previously known tidal tail members.
Within the cluster, we find seven new red giant and one blue horizontal branch
members and confirm a further twelve known red giant members. In total, we
provide velocity data for 67 stars in the cluster and the tidal tails. Using a
maximum likelihood technique, we derive a radial velocity for Pal 5 of $-57.4
\pm 0.3$ km s$^{-1}$ and a velocity dispersion of $1.2\pm0.3$ km s$^{-1}$. We
confirm and extend the linear velocity gradient along the tails of $1.0 \pm
0.1$ km s$^{-1}$ deg$^{-1}$, with an associated intrinsic velocity dispersion
of $2.1\pm0.4$ km s$^{-1}$. Neither the velocity gradient nor the dispersion
change in any significant way with angular distance from the cluster, although
there is some indication that the gradient may be smaller at greater angular
distances in the trailing tail. Our results verify the tails as kinematically
cold structures and will allow further constraints to be placed on the orbit of
Pal 5, ultimately permitting a greater understanding of the shape and extent of
the Galaxy's dark matter halo.
