1995A&A...303..761M

The mean radial velocities obtained with CORAVEL for 151 individual stars located in the center of the galactic globular cluster ω Centauri = NGC 5139 are combined with the previous measurements of 318 other stars to derive the velocity dispersion profile. It increases significantly from the outer parts inwards: the 16 outermost stars, located between 19.2' and 22.4' from the center, have a velocity dispersion σ_p=5.1±1.6km/s, while the 16 innermost stars, located within 1' from the center, have a velocity dispersion σ_p=21.9±3.9km/s. This inner value of about σ_p(0)=22km/s is the largest velocity dispersion value obtained in the core of any galactic globular cluster and is significantly larger than the previous estimate, viz. σ_p=16.7±1.9km/s (Meylan & Mayor 1986). A simultaneous fit of these radial velocities and of the surface brightness profile to a multi-mass King-Michie dynamical model provides mean estimates of the total mass equal to M_tot=5.1x10⁶M_☉, with a corresponding mean mass-to-light ratio M/L_V=4.1. The present results emphasize the fact that ω Centauri is not only the brightest but also, by far, the most massive galactic globular cluster.