Using high-dispersion spectra from the HIRES echelle spectrograph on the Keck I telescope , we measure velocity dispersions for 4 globular clusters in M33 .
Combining the velocity dispersions with integrated photometry and structural parameters derived from King–Michie model fits to WFPC2 images , we obtain mass-to-light ratios for the clusters .
The mean value is \mbox { $M / L _ { V } $ } = 1.53 \pm 0.18 , very similar to the M / L _ { V } of Milky Way and M31 globular clusters .
The M33 clusters also fit very well onto the fundamental plane and binding energy – luminosity relations derived for Milky Way GCs .
Dynamically and structurally , the four M33 clusters studied here appear virtually identical to Milky Way and M31 GCs .