Large-scale assembly bias of dark matter halos

Abstract

We present precise measurements of the assembly bias of dark matter halos,\ni.e. the dependence of halo bias on other properties than the mass, using\ncurved "separate universe" N-body simulations which effectively incorporate an\ninfinite-wavelength matter overdensity into the background density. This method\nmeasures the LIMD (local-in-matter-density) bias parameters $b_n$ in the\nlarge-scale limit. We focus on the dependence of the first two Eulerian biases\n$b^E_1$ and $b^E_2$ on four halo properties: the concentration, spin, mass\naccretion rate, and ellipticity. We quantitatively compare our results with\nprevious works in which assembly bias was measured on fairly small scales.\nDespite this difference, our findings are in good agreement with previous\nresults. We also look at the joint dependence of bias on two halo properties in\naddition to the mass. Finally, using the excursion set peaks model, we attempt\nto shed new insights on how assembly bias arises in this analytical model.\n