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Abstract: We investigate the origin of halo assembly bias, the dependence of haloclustering on assembly history. We relate halo assembly to peak propertiesmeasured in the Lagrangian space of the initial linear Gaussian random densityfield, and show how these same Lagrangian properties determine large-scalebias. We focus on the two regimes where assembly bias has been observed to besignificant: at masses very large and very small compared to the nonlinear massscale. At high masses, we show that assembly bias is expected from thestatistics of the peaks of Gaussian random fluctuations, and we show that theextent of assembly bias found in N-body simulations of rare halos is inexcellent agreement with our theoretical prediction. At low masses, we arguethat assembly bias largely arises from a sub-population of low mass halos whosemass accretion has ceased. Due to their arrested development, these halosnaturally become unbiased, in contrast to their anti-biased peers. We show thata simple toy model incorporating these effects can roughly reproduce the biastrends found in N-body simulations.



Author: Neal Dalal CITA, Martin White Berkeley, J. Richard Bond CITA, Alexander Shirokov CITA

Source: https://arxiv.org/



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