Constraints on $\Omega_\mathrm{m}$ and $\sigma_8$ from the potential-based cluster temperature function

TL;DR

This paper refines a theoretical model for galaxy cluster temperatures based on cosmic potential perturbations, improving agreement with simulations and enabling constraints on cosmological parameters consistent with Planck results.

Contribution

It introduces a refined potential-based temperature function with an improved merger model and redshift-dependent scaling, enhancing the accuracy of cosmological parameter constraints.

Findings

Good agreement with simulation data using the potential-based model.

Better match achieved with redshift-dependent temperature scaling.

Constraints on $\

Abstract

The abundance of galaxy clusters is in principle a powerful tool to constrain cosmological parameters, especially $\Omega_\mathrm{m}$ and $\sigma_8$, due to the exponential dependence in the high-mass regime. While the best observables are the X-ray temperature and luminosity, the abundance of galaxy clusters, however, is conventionally predicted as a function of mass. Hence, the intrinsic scatter and the uncertainties in the scaling relations between mass and either temperature or luminosity lower the reliability of galaxy clusters to constrain cosmological parameters. In this article, we further refine the X-ray temperature function for galaxy clusters by Angrick et al., which is based on the statistics of perturbations in the cosmic gravitational potential and proposed to replace the classical mass-based temperature function, by including a refined analytic merger model and compare the theoretical prediction to results from a cosmological hydrodynamical simulation. Although we find already a good agreement if we compare with a cluster temperature function based on the mass-weighted temperature, including a redshift-dependent scaling between mass-based and spectroscopic temperature yields even better agreement between theoretical model and numerical results. As a proof of concept, incorporating this additional scaling in our model, we constrain the cosmological parameters $\Omega_\mathrm{m}$ and $\sigma_8$ from an X-ray sample of galaxy clusters and tentatively find agreement with the recent cosmic microwave background based results from the Planck mission at 1$\sigma$-level.