ar X iv : a st ro - p h / 99 12 04 1 v 1 2 D ec 1 99 9 Tidal Tails around 20 Galactic Globular Clusters

In addition to the effects of their internal dynamical evolution, globular clusters suffer strong dynamical evolution from the potential well of their host galaxy (Gnedin & Ostriker 1997, Murali & Weinberg 1997). These external forces speed up the internal dynamical evolution of these stellar systems, accelerating their destruction. Shocks are caused by the tidal field of the galaxy: interactions with the disk, the bulge and, somehow, with the giant molecular clouds, heat up the outer regions of each star clusters. The stars in the halo are stripped by the tidal field. All globular clusters are expected to have already lost an important fraction of their mass, deposited in the form of individual stars in the halo of the Galaxy (see Meylan & Heggie 1997 for a review). Recent N-body simulations of globular clusters embedded in a realistic galactic potential (Oh & Lin 1992; Johnston et al. 1999) were performed in order to study the amount of mass loss for different kinds of orbits and different kinds of clusters, along with the dynamics and the mass segregation in tidal tails. Grillmair et al. (1995) in an observational analysis of star counts in the outer parts of a few galactic globular clusters found extra-cluster overdensities that they associated partly with stars stripped into the Galaxy field. We present hereafter our study of the 2-D structures of the tidal tails associated with 20 galactic globular clusters, obtained by using the wavelet transform to detect weak structures at large scale and filter the strong background noise for the low galactic latitude clusters (Leon, Meylan & Combes 1999). We also present N-body simulations of globular clusters in orbits around the Galaxy, in order to study quantitatively and geometrically the tidal effects they encounter (Combes, Leon & Meylan 1999).