Galaxy groups and haloes in the seventh data release of the Sloan Digital Sky Survey

In this work we introduce a new method to perform the identification of groups of galaxies and present results of the identification of galaxy groups in the seventh data release of the Sloan Digital Sky Survey. Our methodology follows an approach that resembles the standard friends-of-friends method. However, it uses assumptions on the mass of the dark matter halo hosting a group of galaxies to link galaxies in the group using a local linking length. Our method does not assume any ad hoc parameter for the identification of groups, nor a linking length or a density threshold. This parameter-free nature of the method and the robustness of its results are the most important points of our work. We describe the data used for our study and give details of the implementation of the method. We obtain galaxy groups and halo catalogues for four volume-limited samples whose properties are in good agreement with previous works. They reproduce the expected stellar mass functions and follow the expected stellarhalo mass relation. We found that most of the stellar content in groups of galaxies comes from objects with Mr absolute magnitudes larger than -19, meaning that it is important to resolve the low-luminosity components of groups of galaxies to acquire detailed information about their properties.