Bibcode
Sollima, A.; Bellazzini, M.; Smart, R. L.; Correnti, M.; Pancino, E.; Ferraro, F. R.; Romano, D.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 396, Issue 4, pp. 2183-2193.
Fecha de publicación:
7
2009
Número de citas
64
Número de citas referidas
56
Descripción
We present the results of a survey of radial velocities over a wide
region extending from r ~= 10 out to 80 arcmin (~1.5 tidal radii) within
the massive star cluster ω Centauri (ω Cen). 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
our previous survey, we assembled a final homogeneous sample of 946
cluster members that allowed us to trace the velocity dispersion profile
from the centre out to r ~ 32 arcmin. The velocity dispersion appears to
decrease monotonically over this range, from a central value of
σv ~ 17.2kms-1 down to a minimum value of
σv ~ 5.2kms-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 ω Cen during the last 10
orbits into the Galactic potential suggests that (i) the rotation of
stars lying in the inner ~=20 arcmin of the clusters is not due to the
effects of the tidal field of the Milky Way, as hypothesized by other
authors and (ii) the overall observational scenario is still compatible
with the possibility that the outer regions of the cluster are subject
to some tidal stirring.
Based on FORS observations collected with the Very Large Telescope at
the European Southern Observatory (ESO), Cerro Paranal, Chile, within
the observing programmes 071.D-0217A and 081.D-0255A.
E-mail: asollima [at] iac.es (asollima[at]iac[dot]es)