CLUMPY SUBSTRUCTURES IN GLOBULAR CLUSTER TIDAL TAILS P. DI MATTEO, R. CAPUZZO DOLCETTA and P. MIOCCHI Department of Physics, Universita ´ di Roma La Sapienza, P.le Aldo Moro 2, 00185 Rome, Italy, e-mail: miocchi@uniroma1.it (Received: 19 May 2005; revised: 29 July 2005; accepted: 9 September 2005) Abstract. In this paper, we present some preliminary results of numerical simulations of a globular cluster orbiting in the inner region of a triaxial galaxy. The formation and evolution of tidal tails around the cluster is discussed, together with their morphology, which shows clumpy substructures as observed, for example, in the galactic globular cluster Palomar 5. Key words: numerical simulations, globular clusters, computational astrophysics 1. Introduction In the recent years, the observational evidence of the interaction of globular clusters (GCs) with the galactic tidal field is rapidly growing. Firstly, Grillmair et al. (1995), using color-magnitude selected star counts in a dozen of galactic GCs, showed that in the outer parts of these clusters the stellar surface density profiles exceeded the prediction of King (1966) models, extending also outside the tidal radius of the corresponding King model. Other results confirmed Grillmair’s findings (Lehmann and Scholz 1997; Leon et al., 2000; Testa et al., 2000; Siegel et al., 2001; Lee et al., 2003); all these works suggest that many GCs are likely surrounded by haloes or tails, made up of stars which were tidally stripped from the system. This was the state of the art until the spectacular findings of two tidal tails emanating from the outer part of the Palomar 5 globular cluster and covering an arc of 10° on the sky, corresponding to a projected length of 4 kpc at the distance of the cluster (Odenkirchen et al., 2001, 2003; see also http://www.sdss.org). Some numerical works have investigated the complex phenomena related to the formation and evolution of clusters tidal tails. Among others, Combes et al. (1999) carried out N-body simulations of GCs moving in a realistic galactic model, in order to determine the geometry and density distribution of tidal tails and to quantify the mass loss from the cluster. They found that in the case of large amount of mass loss, these structures follow the cluster orbit, even if the correlation between the elongation of the tails and the Celestial Mechanics and Dynamical Astronomy (2005) 91: 59–73 Ó Springer 2005