On the universality of the halo mass function beyond ${\Lambda}$CDM cosmology

TL;DR

This study tests the universality of the halo mass function across various cosmological models using high-resolution simulations, finding deviations within 5% for a range of parameters up to redshift 7.

Contribution

It demonstrates that the halo mass function remains approximately universal across different cosmologies with simple parameter variations, using high-resolution N-body simulations.

Findings

Deviations within 5% for parameter variations

Universality holds up to redshift 7

Reference locus constructed from ΛCDM simulation

Abstract

Theoretical frameworks based on Press-Schechter formalism and excursion set arguments suggest that the abundance of dark matter haloes exhibits universal behaviour when expressed in terms of peak height. If true, this implies that a single high-accuracy cosmological simulation could serve as a basis for constructing an emulator applicable to any other cosmology of interest. This tantalising possibility has inspired numerous studies over the years. However, in practice, different ways of defining haloes have led to mixed results concerning this issue. In this work, we utilise a suite of high-resolution cosmological $N$-body simulations, to revisit this question for friends-of-friends haloes under the flat, time-evolving $w$CDM model, with simple modifications of the primordial physics via variations in the scalar spectral index and its running. We construct a reference locus of $\nu f(\nu)$ from our fiducial ${\Lambda}$CDM simulation and compare it against measurements from alternative models. We find that deviations from the locus remain within $5 \%$ when varying each of the parameters within the ranges: ${w_0} = -1.0 \pm 0.1$, $w_a = 0\pm0.2$, $\Omega_{\rm DE} = 0.693\pm0.050$, $\omega_{\rm c} = 0.119\pm0.006$, $\omega_{\rm b} =0.0222\pm0.0011$, $A_{\rm s} = (2.15\pm0.22) \times {10^{-9}}$, $n_{\rm s} =0.961\pm0.048$, $\alpha_{\rm s}\ = 0\pm0.01$, for redshift $z < 7$.