Feeling the pull, a study of natural Galactic accelerometers. II:
  kinematics and mass of the delicate stellar stream of the Palomar 5 globular
  cluster
  We present two spectroscopic surveys of the tidal stellar stream of the
Palomar 5 globular cluster, undertaken with the VLT/FLAMES and AAT/AAOmega
instruments. We use these data in conjunction with photometric data presented
in the previous contribution in this series to classify the survey stars in
terms of their probability of belonging to the Palomar 5 stellar stream. We
find that high-probability candidates are only found in a very narrow spatial
interval surrounding the locus of the stream on the sky. PanSTARRS RRLyrae
stars in this region of sky are also distributed in a similar manner. The
absence of significant "fanning" of this stellar stream confirms that Palomar 5
does not follow a chaotic orbit. Previous studies have found that Palomar 5 is
largely devoid of low-mass stars, and we show that this is true also of the
stellar populations along the trailing arm out to $6\deg$. Within this region,
which contains 73\% of the detected stars, the population is statistically
identical to the core, implying that the ejection of the low-mass stars
occurred before the formation of the stream. We also present an updated
structural model fit to the bound remnant, which yields a total mass of
$4297\pm98 {\rm\,M_\odot}$ and a tidal radius $0.145\pm0.009$ kpc. We estimate
the mass of the observed system including the stream to be $12200\pm400
{\rm\,M_\odot}$, and the initial mass to have been $\sim47000\pm1500
{\rm\,M_\odot}$. These observational constraints will be employed in our next
study to model the dynamics of the system in detail.
