Impact of the calibration of the Halo Mass Function on galaxy cluster number count cosmology

TL;DR

This paper investigates how uncertainties in the halo mass function affect cosmological constraints from galaxy cluster surveys, highlighting the need for improved HMF precision for future large-scale surveys.

Contribution

It quantifies the impact of HMF parameter uncertainties on cosmological constraints across current and future galaxy cluster surveys.

Findings

Current HMF uncertainties do not significantly affect Planck-like surveys.

HMF uncertainties can greatly degrade constraints for Euclid-like surveys.

Improving HMF parameter precision is essential for future large surveys.

Abstract

The halo mass function (HMF) is a critical element in cosmological analyses of galaxy cluster catalogs. We quantify the impact of uncertainties in HMF parameters on cosmological constraints from cluster catalogs similar to those from Planck, those expected from the Euclid, Roman and Rubin surveys, and from a hypothetical larger future survey. We analyse simulated catalogs in each case, gradually loosening priors on HMF parameters to evaluate the degradation in cosmological constraints. While current uncertainties on HMF parameters do not substantially impact Planck-like surveys, we find that they can significantly degrade the cosmological constraints for a Euclid-like survey. Consequently, the current precision on the HMF will not be sufficient for Euclid (or Roman or Rubin) and possible larger surveys. Future experiments will have to properly account for uncertainties in HMF parameters, and it will be necessary to improve precision of HMF fits to avoid weakening constraints on cosmological parameters.