The luminosity function of diverse satellite galaxy systems

The high-resolution, SPH galaxies of the McMaster Unbiased Galaxy Survey (MUGS) are used to examine the satellite systems of sixteen model host galaxies. Each galaxy has a different mass, angular momentum and merger history that yield a rich set of satellite luminosity functions. With new observations of distant satellite systems, we can compare these luminosity functions to satellite systems beyond the Local Group. We find that the luminosity functions of our simulations compare well to observations when the luminosity functions are scaled according to host mass. We use the recently-found relationship between dwarf satellites and host mass in distant satellite systems (Trentham & Tully 2009) to normalize a theoretical, complete luminosity function for the Milky Way (Koposov et al. 2008). The luminosity function of satellites, expressed as a function of the host mass, is given by dN/dM_V= 3.5 x M_host^(0.91) x 10^(0.1 x M_V-10.2), where host mass is given in M_sun. The mass of a host galaxy can be used to predict the number of dwarf satellites and even when considering spiral and elliptical hosts separately this relation holds.