The Connection between Galaxies and Dark Matter Structures in the Local
  Universe
  We provide new constraints on the connection between galaxies in the local
universe, identified by the Sloan Digital Sky Survey (SDSS), and dark matter
halos and their constituent substructures in the $\Lambda$CDM model using WMAP7
cosmological parameters. Predictions for the abundance and clustering
properties of dark matter halos, and the relationship between dark matter hosts
and substructures, are based on a high-resolution cosmological simulation, the
Bolshoi simulation. We associate galaxies with halos and subhalos using subhalo
abundance matching, performing a comprehensive analysis which investigates the
underlying assumptions of this technique including (a) which halo property is
most closely associated with galaxy stellar masses and luminosities, (b) how
much scatter is in this relationship, and (c) how much subhalos can be stripped
before their galaxies are destroyed. The models are jointly constrained by new
measurements of the projected two-point galaxy clustering and the observed
conditional stellar mass function of galaxies in groups. The data put tight
constraints on the satellite fraction of galaxies as a function of galaxy
stellar mass, on the scatter between halo and galaxy properties, and on the
underlying conditional stellar mass function. These data rule out several halo
properties commonly used in abundance matching, largely because the satellite
fractions in the models disagree with those data. We show that an abundance
matching model that associates galaxies with the peak circular velocity of
their halos is in good agreement with the data, when scatter of $0.20 \pm 0.03$
dex in stellar mass at a given peak velocity is included. This will yield
important constraints for galaxy formation models, and also provides
encouraging indications that the galaxy--halo connection can be modeled with
sufficient fidelity for future precision studies of the dark Universe.
