The Mass and Stellar Content of the Globular Cluster M13
Abstract
Kinematical information has been used to solve the Jeans equation to provide mass estimates in the globular cluster M13. Since the cluster has been the subject of both proper motion and radial velocity studies, it is possible to compare mass estimates based on velocity dispersion profiles derived from the two types of data. It is found that the proper motions provide a much more constrained mass estimate than do the radial velocities, which is due to the fundamental fact that two independent velocity dispersion profiles are required to solve the spherical Jeans equation. The best estimate of the mass inside a spherical shell centered on the cluster with a radius corresponding to 390 arcsec on the sky is about 600,000 solar masses. A comparison of the dynamical mass estimate with a Michie-King model of M13 suggests that much of the cluster mass (perhaps 50 percent) may be in the form of low-mass stars and brown dwarfs.
- Publication:
-
The Astronomical Journal
- Pub Date:
- December 1992
- DOI:
- 10.1086/116386
- Bibcode:
- 1992AJ....104.2104L
- Keywords:
-
- Brown Dwarf Stars;
- Globular Clusters;
- Stellar Mass;
- Astronomical Models;
- Mass To Light Ratios;
- Radial Velocity;
- Stellar Luminosity;
- Stellar Motions;
- Astrophysics;
- GLOBULAR CLUSTERS: INDIVIDUAL: M13