The mass-to-light ratios of extragalactic globular clusters

Measurements of the systemic velocity and velocity dispersion of 14 globular clusters in Andromeda have been made from integrated-light spectra observed at 9 km s-1 resolution. Systemic velocities are good to ± 4 km s-1 on an absolute scale. The velocity dispersions increase with integrated cluster absolute magnitude, as do dispersions of concentrated clusters in our Galaxy. In Andromeda, dispersions as high as 40 km s-1 are seen. In two cases, individual estimates of mass-to-light ratio can be made using effective radii measured recently by a previous author. These suggest that the mean mass-to-light ratio is 2±1 times that of globular clusters in our Galaxy. (author)