## Detalles de publicación

PP 06008

## Merging of Elliptical Galaxies as Possible Origin of the Intergalactic Stellar Population

(1) National Optical Astronomy Observatory, (2) IAC

We present N-body simulations of elliptical galaxy encounters into dry mergers to study the resulting unbound intergalactic stellar population, in particular that of the post-Main Sequence stars. The systems studied are pairs of spherical galaxies without dark halos. The stellar content of the model galaxies is distributed into mass-bins representing low- and intermediate-mass stars (0.85-8 solar masses) according to Salpeter's initial mass function. Our models follow the dynamical evolution of galaxy encounters colliding head-on from initial low-energy parabolic or high-energy mildly-hyperbolic orbits, and for a choice of initial-mass ratios. The merging models with initial parabolic orbits have $M_2/M_1=1$ and 10, and the y leave behind respectively $5.5\%$ and $10\%$ of the total initial mass as unbound stellar mass. The merging model with initial hyperbolic orbit has $M_2/M_1=1$, and leaves behind $21\%$ of its initial stellar mass as unbound mass, showing that the efficiency in producing intergalactic stars through a high-energyhyperbolic encounter is about four times than through a parabolic encounter of the same initial mass ratio. By assuming that all progenitor galaxies as well as the merger remnants are homologous systems we obtained that the intergalactic starlight is $17\%$ and $28\%$ of the total starlight respectively for the parabolic and hyperbolic encounters with $M_2/M_1=1$. In all models, different mass stars have the same probability of becoming unbound and feeding the intergalactic stellar population.