paper

Assembly bias in the local PNG halo bias and its implication for constraints

arXiv:2209.07251 · doi:10.1088/1475-7516/2023/01/023

Abstract

We use -body simulations to study halo assembly bias (i.e., the dependence of halo clustering on properties beyond total mass) in the density and primordial non-Gaussianity (PNG) linear bias parameters and , respectively. We consider concentration, spin and sphericity as secondary halo properties, for which we find a clear detection of assembly bias for and . At fixed total mass, halo spin and sphericity impact and in a similar manner, roughly preserving the shape of the linear relation satisfied by the global halo population. Halo concentration, however, drives and in opposite directions. This induces significant changes to the relation, with higher concentration halos having higher amplitude of . For and in particular, the population comprising either all halos, those with the lowest or those with the highest concentrations have a PNG bias of , and , respectively. Varying the halo concentration can make very small and even change its sign. These results have important ramifications for galaxy clustering constraints of the local PNG parameter that assume fixed forms for the relation. We illustrate the significant impact of halo assembly bias in actual data using the BOSS DR12 galaxy power spectrum: assuming that BOSS galaxies are representative of all halos, the lowest or the highest concentration halos yields , respectively. Our results suggest taking host halo concentration into account in galaxy selection strategies to maximize the signal-to-noise on . They also motivate more simulation-based efforts to study the relation of halos and galaxies.

21 pages, 4 figures, comments welcome; V2 minor modifications throughout, published in JCAP

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