SCYON Abstract

Received on March 28 2006

The dynamical M/L-profile and distance of the globular cluster M15

AuthorsRemco van den Bosch, Tim de Zeeuw, Karl Gebhardt, Eva Noyola, Glenn van de Ven
Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, Netherlands.
Astronomy Department, University of Texas at Austin, Austin, TX 78712.
Accepted byAstrophysical Journal


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+/-15 degrees, a dynamical distance of 10.3+/-0.4 kpc and an M/L profile with a central peak. The inferred mass in the central 0.05 parsec is 3400 M(sun), implying a central density of at least 7.4x106 M(sun) pc-3. We cannot 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.