Globular Clusters Dynamics in a Galactic Tidal Field
Paola Di MATTEO
Observatoire de Paris/LERMA
Résumé :
Since Shapley's pioneering work, globular clusters
(GCs) have played a key role in our understanding
of the Universe and of the manner in which our
Galaxy formed. They are the best systems for studying
stellar dynamics, having relaxation times smaller than
their age, so that, at least in the core, stars
are expected to have lost memory of their initial
conditions. Together with internal processes,
also perturbations due to an external field (in particular,
shocks due to the passage through the Galactic
disk and to the interaction with the bulge) can
significantly affect the evolution of a GC. Indeed,
it is commonly accepted that the present
GC population represents the survivor of an initially
more numerous one, depopulated by many disruptive
processes.
In the last decade, many observational evidences
of the interaction of GCs with the tidal field
have been found, suggesting that many GCs are likely
surrounded by halos or tails made up of stars that were
tidally stripped from these systems. The detection of
tidal tails gives not only strong support to the
hypothesis that GCs have already lost an important
fraction of their mass, probably now deposited in
the form of individual stars in the halo of the Galaxy;
it is also fundamental to obtain constraints
on the GC local orbits, usually unknown unless
contemporary available data on proper motions and
radial velocities.
In this seminar, I will present and discuss
the results obtained by means of detailed numerical
simulations of globular clusters orbiting in the
tidal field of a triaxial galaxy. In particular,
the formation and evolution of tidal tails outside
the cluster limiting radius will be investigated,
in order to understand to what extent it is possible
to reconstruct the GC orbits from the elongation
of their tidal streams.
