The Dependence of Halo Clustering on Halo Formation History, Concentration, and Occupation

We investigate the dependence of dark matter halo clustering on haloformation time, density profile concentration, and subhalo occupation number,using high-resolution numerical simulations of a LCDM cosmology. We confirmresults that halo clustering is a function of halo formation time, and thatthis trend depends on halo mass. For the first time, we show unequivocally thathalo clustering is a function of halo concentration and show that thedependence of halo bias on concentration, mass, and redshift can be accuratelyparameterized in a simple way: b(c,M|z) = b(M|z) b(c|M/M*). The scaling betweenbias and concentration changes sign with the value of M/M*: high concentration(early forming) objects cluster more strongly for M <~ M* while lowconcentration (late forming) objects cluster more strongly for rare high-masshalos, M >~ M*. We show the first explicit demonstration that host dark haloclustering depends on the halo occupation number (of dark matter subhalos) anddiscuss implications for halo model calculations of dark matter power spectraand galaxy clustering statistics. The effect of these halo properties onclustering is strongest for early-forming dwarf-mass halos, which aresignificantly more clustered than typical halos of their mass. Our resultssuggest that isolated low-mass galaxies (e.g. low surface-brightness dwarfs)should have more slowly-rising rotation curves than their clusteredcounterparts, and may have consequences for the dearth of dwarf galaxies invoids. They also imply that self calibrating richness-selected cluster sampleswith their clustering properties might overestimate cluster masses and biascosmological parameter estimation.Comment: 13 pages, 6 figures; Figure 3 best viewed in color, ApJ in press (replaced to match accepted version, updated literature discussion