Galaxy groups and haloes in the SDSS-DR7
  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 (SDSS-DR7). Our
methodology follows an approach that resembles the standard friends-of-friends
(FoF) 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 assumes 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 catalogs for
four volume limited samples whose properties are in good agreement with
previous works. They reproduces the expected stellar mass functions and follow
the expected stellar-halo mass relation. We found that most of the stellar
content in groups of galaxies comes from objects with $M_r$ 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.
