We construct orbit-based axisymmetric dynamical models for the globular cluster M15 which fit groundbased line-of-sight velocities and Hubble Space Telescope line-of-sight velocities and proper motions .
This allows us to constrain the variation of the mass-to-light ratio M / L as a function of radius in the cluster , and to measure the distance and inclination of the cluster .
We obtain a best-fitting inclination of 60 ^ { \circ } \pm 15 ^ { \circ } , a dynamical distance of 10.3 \pm 0.4 kpc and an M / L profile with a central peak .
The inferred mass in the central 0.05 parsec is 3400 \ > { M _ { \odot } } , implying a central density of at least 7.4 \times 10 ^ { 6 } \ > { M _ { \odot } } pc ^ { -3 } .
We can not distinguish the nature of the central mass concentration .
It could be an IMBH or it could be large number of compact objects , or it could be a combination .
The central 4 arcsec of M15 appears to contain a rapidly spinning core , and we speculate on its origin .