Cosmological Constraints from Galaxy Clustering and the Mass-to-Number Ratio of Galaxy Clusters: Marginalizing over the Physics of Galaxy Formation

TL;DR

This paper demonstrates that combining galaxy clustering with the mass-to-number ratio of galaxy clusters can reliably constrain cosmological parameters like $\

Contribution

It introduces a method that marginalizes over galaxy formation uncertainties to accurately estimate cosmological parameters from galaxy data.

Findings

The method successfully recovers $\

It is robust across different galaxy formation models.

It effectively marginalizes over Halo Occupation Distribution parameters.

Abstract

Many approaches to obtaining cosmological constraints rely on the connection between galaxies and dark matter. However, the distribution of galaxies is dependent on their formation and evolution as well as the cosmological model, and galaxy formation is still not a well-constrained process. Thus, methods that probe cosmology using galaxies as a tracer for dark matter must be able to accurately estimate the cosmological parameters without knowing the details of galaxy formation a priori. We apply this reasoning to the method of obtaining $\Omega_m$ and $\sigma_8$ from galaxy clustering combined with the mass-to-number ratio of galaxy clusters. To test the sensitivity of this method to variations due to galaxy formation, we consider several different models applied to the same cosmological dark matter simulation. The cosmological parameters are then estimated using the observables in each model, marginalizing over the parameters of the Halo Occupation Distribution (HOD). We find that for models where the galaxies can be well represented by a parameterized HOD, this method can successfully extract the desired cosmological parameters for a wide range of galaxy formation prescriptions.