We present the results of a survey of radial velocities over a wide region extending from r \simeq 10 \arcmin out to r \simeq 80 \arcmin ( \sim 1.5 tidal radii ) within the massive star cluster \omega Centauri .
The survey was performed with FLAMES @ VLT , to study the velocity dispersion profile in the outer regions of this stellar system .
We derived accurate radial velocities for a sample of 2557 newly observed stars , identifying 318 bona-fide cluster red giants .
Merging our data with those provided by Pancino et al .
( 2007 ) , we assembled a final homogeneous sample of 946 cluster members that allowed us to trace the velocity dispersion profile from the center out to r \sim 32 arcmin .
The velocity dispersion appears to decrease monotonically over this range , from a central value of \sigma _ { v } \sim~ { } 17.2 ~ { } Km~ { } s ^ { -1 } down to a minimum value of \sigma _ { v } \sim~ { } 5.2 ~ { } Km~ { } s ^ { -1 } .
The observed surface brightness profile , rotation curve , velocity dispersion profile and ellipticity profile are simultaneously well reproduced by a simple dynamical model in which mass follows light , within the classical Newtonian theory of gravitation .
The comparison with an N-body model of the evolution of a system mimicking \omega Cen during the last 10 orbits into the Galactic potential suggests that ( a ) the rotation of stars lying in the inner \simeq 20 \arcmin of the clusters is not due to the effects of the tidal field of the Milky Way , as hypothized by other authors , and ( b ) the overall observational scenario is still compatible with the possibility that the outer regions of the cluster are subject to some tidal stirring .