A redefinition of the halo boundary leads to a simple yet accurate halo model of large-scale structure
Monthly Notices of the Royal Astronomical Society, 2021•academic.oup.com
We present a model for the halo–mass correlation function that explicitly incorporates halo
exclusion and allows for a redefinition of the halo boundary in a flexible way. We assume
that haloes trace mass in a way that can be described using a single scale-independent bias
parameter. However, our model exhibits scale-dependent biasing due to the impact of halo-
exclusion, the use of a 'soft'(ie not infinitely sharp) halo boundary, and differences in the one
halo term contributions to ξhm and ξmm. These features naturally lead us to a redefinition of�…
exclusion and allows for a redefinition of the halo boundary in a flexible way. We assume
that haloes trace mass in a way that can be described using a single scale-independent bias
parameter. However, our model exhibits scale-dependent biasing due to the impact of halo-
exclusion, the use of a 'soft'(ie not infinitely sharp) halo boundary, and differences in the one
halo term contributions to ξhm and ξmm. These features naturally lead us to a redefinition of�…
Abstract
We present a model for the halo–mass correlation function that explicitly incorporates halo exclusion and allows for a redefinition of the halo boundary in a flexible way. We assume that haloes trace mass in a way that can be described using a single scale-independent bias parameter. However, our model exhibits scale-dependent biasing due to the impact of halo-exclusion, the use of a ‘soft’ (i.e. not infinitely sharp) halo boundary, and differences in the one halo term contributions to ξhm and ξmm. These features naturally lead us to a redefinition of the halo boundary that lies at the ‘by eye’ transition radius from the one-halo to the two-halo term in the halo–mass correlation function. When adopting our proposed definition, our model succeeds in describing the halo–mass correlation function with residuals over the radial range 0.1 h−1 Mpc < r < 80 h−1 Mpc, and for halo masses in the range 1013 h−1 M⊙ < M < 1015 h−1 M⊙. Our proposed halo boundary is related to the splashback radius by a roughly constant multiplicative factor. Taking the 87 percentile as reference we find rt/Rsp ≈ 1.3. Surprisingly, our proposed definition results in halo abundances that are well described by the Press–Schechter mass function with δsc�= 1.449���0.004. The clustering bias parameter is offset from the standard background-split prediction by . This level of agreement is comparable to that achieved with more standard halo definitions.
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