We analyze line-of-sight velocity and proper motion data of stars in the Galactic globular cluster M15 using a new method to fit dynamical models to discrete kinematic data .
Our fitting method maximizes the likelihood for individual stars and , as such , does not suffer the same loss of spatial and velocity information incurred when spatially binning data or measuring velocity moments .
In this paper , we show that the radial variation in M15 of the mass-to-light ratio is consistent with previous estimates and theoretical predictions , which verifies our method .
Our best-fitting axisymmetric Jeans models do include a central dark mass of \sim 2 \pm 1 \cdot 10 ^ { 3 } M _ { \odot } , which can be explained by a high concentration of stellar remnants at the cluster center .
This paper shows that , from a technical point of view and with current computing power , spatial binning of data is no longer necessary .
This not only leads to more accurate fits , but also avoids biased mass estimates due to the loss of resolution .
Furthermore , we find that the mass concentration in M15 is significantly higher than previously measured , and is in close agreement with theoretical predictions for core-collapsed globular clusters without a central intermediate-mass black hole .