We present Keck/DEIMOS spectroscopy and CFHT/MegaCam photometry for the Milky Way globular cluster Palomar 13 .
We triple the number of spectroscopically confirmed members , including many repeat velocity measurements .
Palomar 13 is the only known globular cluster with possible evidence for dark matter , based on a Keck/HIRES 21 star velocity dispersion of \sigma = 2.2 \pm 0.4 km s ^ { -1 } .
We reproduce this measurement , but demonstrate that it is inflated by unresolved binary stars .
For our sample of 61 stars , the velocity dispersion is \sigma = 0.7 ^ { +0.6 } _ { -0.5 } km s ^ { -1 } .
Combining our DEIMOS data with literature values , our final velocity dispersion is \sigma = 0.4 ^ { +0.4 } _ { -0.3 } km s ^ { -1 } .
We determine a spectroscopic metallicity of [ Fe/H ] = -1.6 \pm 0.1 dex , placing a 1-sigma upper limit of \sigma _ { [ Fe / H ] } \sim 0.2 dex on any internal metallicity spread .
We determine Palomar 13 ’ s total luminosity to be M _ { V } = -2.8 \pm 0.4 , making it among the least luminous known globular clusters .
The photometric isophotes are regular out to the half-light radius and mildly irregular outside this radius .
The outer surface brightness profile slope is shallower than typical globular clusters ( \Sigma \propto~ { } r ^ { \eta } , \eta = -2.8 \pm 0.3 ) .
Thus at large radius , tidal debris is likely affecting the appearance of Palomar 13 .
Combining our luminosity with the intrinsic velocity dispersion , we find a dynamical mass of of M _ { 1 / 2 } = 1.3 ^ { +2.7 } _ { -1.3 } \times 10 ^ { 3 } M _ { \odot } and a mass-to-light ratio of M / L _ { V } = 2.4 ^ { +5.0 } _ { -2.4 } M _ { \odot } / L _ { \odot } .
Within our measurement errors , the mass-to-light ratio agrees with the theoretical predictions for a single stellar population .
We conclude that , while there is some evidence for tidal stripping at large radius , the dynamical mass of Palomar 13 is consistent with its stellar mass and neither significant dark matter , nor extreme tidal heating , is required to explain the cluster dynamics .