Mass-to-Light Ratios for Globular Clusters. II. The Low-Concentration Clusters NGC 288, NGC 5466, and M55 (NGC 6809)

Radial velocities accurate to about 1 km/s are measured for 20-30 stars in each of the three low-concentration globular clusters NGC 288, NGC 5466, and M55 in order to calculate the velocity dispersions and mass-to-light ratios (MLRs) for these clusters, which are used to investigate their stellar populations. Single- and multicomponent King models are adapted to the present velocity data and to surface-brightness profiles taken from the literature. The MLRs of NGC 288, NGC 5466, and M55 do not differ significantly from one another or from those of the cluster population as a whole. The MLR of NGC 288 is lower than would be expected for a cluster that had a power law initial mass function as shallow as the observed present-day main-sequence mass function. Models with initial mass functions consisting of two power law segments fit NGC 288 best when 50 to 70 percent of the cluster mass is in stellar remnants.