Mass-To-Light Ratios For Globular Clusters. III. M107 (NGC 6171; GC1629-129)

We have measured radial velocities accurate to about 1 km s^-1 for 76 stars located within 7 arcmin of the center of the globular cluster M107 (NGC 6171; GC1629-129). Nine of these stars are probably nonmembers and are excluded from the subsequent analysis. We find no signature of rotation greater than our 2 km s^-1 detection threshold. The velocity dispersion decreases with radius, but this change is only about 1.3 times its uncertainty. We have fitted single- and multicomponent King models to our velocity data and to existing surface-brightness profiles. The multicomponent models have a power law or the galactic disk mass function. The single-component models imply that M107 has a mass-to-light ratio, M/L_v, of 1.8 +/- 0.4, in solar units. The best-fitting multicomponent King models have an isotropic or anisotropic (r_a = 10) velocity dispersion tensor and x = 0.67. These models yield a projected central mass-to-light ratio, (M/L_v)(0), of 2.0 +/- 0.4 and a global M/L_v of 1.8 +/- 0.4. The isotropic model with x = 1.35 is also an acceptable, though poorer, fit and yields (M/L_v) (0) of 1.6 +/- 0.3 and M/L_v of 2.7 +/- 0.5. We have rejected models with the galactic disk initial mass function because their dynamical and population M/L's disagree. This suggests that the galactic disk and M107 initial mass functions were different.