Halo occupation distribution (HOD) modelling of high redshift galaxies using the BlueTides simulation

We construct halo occupation distribution (HOD) models of high redshift (z greater than or similar to 7.5) galaxies with M-* > 10(8) M-circle dot h(-1) using the BlueTides hydrodynamic simulation suite, with a particular emphasis on modelling the small scale / 1-halo clustering (0.01 less than or similar to r less than or similar to 1h(-1) Mpc). Similar to low redshift studies, we find that the central and satellite mean HODs (< N-cen > and < N-sat >) can be modelled by a smoothed step function and a power law, respectively. The number density of satellite galaxies is however significantly suppressed compared to low redshift (satellite fractions drop from similar to 50 per cent at z = 0 to less than or similar to 10 per cent at z = 7.5). The mean number of satellites < N-sat > < 1 for halo masses below 3 x 10(11) M-circle dot h(-1) (a rare halo at these redshifts). For the radial number density profiles, satellites with 10(8) less than or similar to M-* less than or similar to 10(9) M-circle dot h(-1) in haloes with MH greater than or similar to 3 x 10(11) M-circle dot h(-1) are consistent with NFW (Navarro, Frenk & White profile with concentrations csat similar to 10-40). Within haloes of mass M-H less than or similar to 3 x 10(11) M-circle dot h(-1), satellites exhibit a power-law profile with slope of -3. Because these haloes dominate the small-scale clustering, the resulting 1-halo term is steeper than predicted using standard NFW profiles. Using this power-law profile for satellites, we can successfully reproduce the small-scale clustering exhibited by BlueTides galaxies using HOD modelling. We predict the highest probability of detecting satellites at z > 7.5 is around centrals of M* similar to 3 x 10(10) M-circle dot h(-1) (with M* greater than or similar to a few 10(7) M-circle dot h(-1)). This should be achievable with the James Webb Space Telescope.