The luminosity function of diverse satellite galaxy systems

TL;DR

This study uses high-resolution simulations to analyze satellite galaxy luminosity functions across various host galaxy masses, comparing results with observations and providing a predictive relation for satellite counts based on host mass.

Contribution

It introduces a normalized luminosity function for satellite galaxies that accounts for host mass, validated against observational data and applicable to different galaxy types.

Findings

Luminosity functions from simulations match observations when scaled by host mass.

A new formula predicts satellite numbers based on host galaxy mass.

The relation holds for both spiral and elliptical host galaxies.

Abstract

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.