The dark side of galaxy stellar populations I: The stellar-to-halo mass
  relation and the velocity dispersion - halo mass relation
  The growth and properties of galaxies are thought to be closely connected to
the ones of their host dark matter halos. Despite the importance of this
so-called galaxy-halo connection, the potential role of dark matter halos in
regulating observed galaxy properties remains yet to be fully understood. In
this work, we derive the ages, metallicites and [Mg/Fe] abundances from optical
spectra from the Sloan Digital Sky Survey of nearby central galaxies, and study
them in terms of their host halos. We investigate how the scatter in the
stellar-to-halo mass relation and the velocity dispersion - halo mass relation
correlates with these stellar population parameters. In addition, we also study
the differences when distinguishing between different galaxy morphologies and
environments. We find that the ages and chemical enrichment of galaxies are not
fully determined by their stellar masses or velocity dispersion, but also
depend on the mass of the host halos. Our findings suggest that the velocity
dispersion is the best proxy of the stellar population parameters with halo
mass playing a secondary yet noticeable role. We interpret that the origin of
the correlation between the scatter of these relations and the ages and
metallicities might be related to different halo formation times.
