The Mass and Halo Dispersion Profile of M32
Abstract
Radial velocities are determined for 15 planetary nebulae in the halo of M32 and used to put constraints on the form of the stellar orbits and on the mass. A technique is developed to test the compatibility of these velocities with trial velocity-dispersion profiles, applying the models of Jaffe (1983) and Merritt (1985) with varying amounts of anisotropy. Assuming constant M/L with radius, the data favor an isotropic dispersion tensor in the halo. The resulting mass is 7.0 x 10 to the 8th solar mass for a Jaffe model galaxy and 9.4 x 10 to the 8th solar mass for a de Vaucouleurs model. These correspond to M/L(B) values of 2.8 and 3.7, respectively. The data indicate that a significantly increasing M/L with radius is likely only if the stars are on highly radial orbits.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1986
- DOI:
- 10.1086/164274
- Bibcode:
- 1986ApJ...305..600N
- Keywords:
-
- Elliptical Galaxies;
- Galactic Structure;
- Halos;
- Local Group (Astronomy);
- Mass To Light Ratios;
- Stellar Orbits;
- Eddington Approximation;
- Line Of Sight;
- Planetary Nebulae;
- Radial Velocity;
- Astrophysics;
- GALAXIES: INDIVIDUAL MESSIER NUMBER: M32;
- GALAXIES: INTERNAL MOTIONS;
- GALAXIES: LOCAL GROUP;
- GALAXIES: STRUCTURE;
- NEBULAE: PLANETARY;
- RADIAL VELOCITIES