The Satellite Luminosity Functions of Galaxies in SDSS

TL;DR

This study analyzes the satellite galaxy luminosity functions around isolated galaxies using SDSS data, revealing that such primaries have about half as many bright satellites as the Milky Way and M31.

Contribution

It provides the first robust statistical measurement of satellite luminosity functions extending 8 magnitudes fainter than primaries using SDSS data.

Findings

Isolated primaries have about half as many satellites brighter than M_V=-14 compared to the Milky Way and M31.

Satellite luminosity functions vary with primary galaxy properties such as luminosity, colour, and concentration.

Stacking ~20,000 systems yields statistically significant results on satellite distributions.

Abstract

We study the luminosity function of satellite galaxies around isolated primaries using the Sloan Digital Sky Survey (SDSS) spectroscopic and photometric galaxy samples. We select isolated primaries from the spectroscopic sample and search for potential satellites in the much deeper photometric sample. For primaries of similar luminosity to the Milky Way and M31, we are able to stack as many as $\sim\negthinspace 20,000$ galaxy systems to obtain robust statistical results. We derive the satellite luminosity function extending almost 8 magnitudes fainter than the primary galaxy. We also determine how the satellite luminosity function varies with the luminosity, colour and concentration of the primary. We find that, in the mean, isolated primaries of comparable luminosity to the Milky Way and M31 contain about a factor of two fewer satellites brighter than $M_V=-14$ than the average of the Milky Way and M31.