Satellites of simulated galaxies: survival, merging and their relationto the dark and stellar haloes

We study the population of satellite galaxies formed in a suite of N-body/gasdynamical simulations of galaxy formation in a ΛCDM universe. The simulations resolve the ∼ 10 most luminous satellites around each host, and probe systems up to six or seven magnitudes fainter than the primary. We find little spatial or kinematic bias between the dark matter and the satellite population. The radius containing half of all satellites is comparable to the half-mass radius of the dark matter component, and the velocity dispersion of the satellites is a good indicator of the virial velocity of the halo; σsat/Vvir ∼ 0.9 ±0.2. Applied to the Local Group, this result suggests that the virial velocity of the Milky Way and M31 might be substantially ∼ 109 ± 22 km/s and