A tale of two populations: the stellar mass of central and satellite
  galaxies
  We develop a new empirical methodology to study the relation between the
stellar mass of galaxies and the mass of their host subhaloes. Our approach is
similar to abundance matching, and is based on assigning a stellar mass to each
subhalo within a large cosmological N-body simulation. However, we
significantly extend the method to include a different treatment for central
and satellite galaxies, allowing the stellar mass of satellite galaxies to
depend on both the host subhalo mass, and on the halo mass. Unlike in previous
studies, our models are constrained by two observations: the stellar mass
function of galaxies, and their auto-correlation functions (CFs). We present
results for ~10^6 different successful models, showing that the uncertainty in
the host subhalo mass reaches a factor of ~10 for a given stellar mass. Our
results thus indicate that the host subhalo mass of central and satellite
galaxies is poorly constrained by using information coming solely from the
abundance and CFs of galaxies. In addition, we demonstrate that the fraction of
stellar mass relative to the universal baryon fraction can vary between
different models, and can reach ~0.6 for a specific population of low mass
galaxies. We conclude that additional observational constraints are needed, in
order to better constrain the mass relation between haloes and galaxies. These
might include weak lensing, satellite kinematics, or measures of clustering
other than the CFs. Moreover, CFs based on larger surveys with a better
estimate of the systematic uncertainties are needed.
