Extensions to the halo occupation distribution model for more accurate
  clustering predictions
  We test different implementations of the halo occupation distribution (HOD)
model to reconstruct the spatial distribution of galaxies as predicted by a
publicly available semi-analytical model (SAM). We compare the measured
two-point correlation functions of the HOD mock catalogues and the SAM samples
to quantify the fidelity of the reconstruction. We use fixed number density
galaxy samples selected according to stellar mass or star formation rate (SFR).
We develop three different schemes to populate haloes with galaxies with
increasing complexity, considering the scatter of the satellite HOD as an
additional parameter in the modelling. We first modify the SAM output, removing
assembly bias and using a standard Navarro-Frenk-White density profile for the
satellite galaxies as the target to reproduce with our HOD mocks. We find that
all models give similar reproductions of the two-halo contribution to the
clustering signal, but there are differences in the one-halo term. In
particular, the HOD mock reproductions work equally well using either the HOD
of central and satellites separately or using a model that also accounts for
whether or not the haloes contain a central galaxy. We find that the HOD
scatter does not have an important impact on the clustering predictions for
stellar mass selected samples. For SFR selections, we obtain the most accurate
results assuming a negative binomial distribution for the number of satellites
in a halo. The scatter in the satellites HOD is a key consideration for HOD
mock catalogues that mimic ELG or SFR selected samples in future galaxy
surveys.
