The 6dF Galaxy Survey: Dependence of halo occupation on stellar mass
  In this paper we study the stellar-mass dependence of galaxy clustering in
the 6dF Galaxy Survey. The near-infrared selection of 6dFGS allows more
reliable stellar mass estimates compared to optical bands used in other galaxy
surveys. Using the Halo Occupation Distribution (HOD) model, we investigate the
trend of dark matter halo mass and satellite fraction with stellar mass by
measuring the projected correlation function, $w_p(r_p)$. We find that the
typical halo mass ($M_1$) as well as the satellite power law index ($\alpha$)
increase with stellar mass. This indicates, (1) that galaxies with higher
stellar mass sit in more massive dark matter halos and (2) that these more
massive dark matter halos accumulate satellites faster with growing mass
compared to halos occupied by low stellar mass galaxies. Furthermore we find a
relation between $M_1$ and the minimum dark matter halo mass ($M_{\rm min}$) of
$M_1 \approx 22\,M_{\rm min}$, in agreement with similar findings for SDSS
galaxies. The satellite fraction of 6dFGS galaxies declines with increasing
stellar mass from 21% at $M_{\rm stellar} = 2.6\times10^{10}h^{-2}\,M_{\odot}$
to 12% at $M_{\rm stellar} = 5.4\times10^{10}h^{-2}\,M_{\odot}$ indicating that
high stellar mass galaxies are more likely to be central galaxies. We compare
our results to two different semi-analytic models derived from the Millennium
Simulation, finding some disagreement. Our results can be used for placing new
constraints on semi-analytic models in the future, particularly the behaviour
of luminous red satellites. Finally we compare our results to studies of halo
occupation using galaxy-galaxy weak lensing. We find good overall agreement,
representing a valuable crosscheck for these two different tools of studying
the matter distribution in the Universe.
