Constraining the halo mass function with observations

TL;DR

This paper evaluates how well current and upcoming surveys can observationally constrain the halo mass function, which is crucial for understanding structure formation and testing cosmological models.

Contribution

It demonstrates that galaxy surveys like DES, Euclid, and J-PAS can provide meaningful observational constraints on the halo mass function, complementing simulations.

Findings

DES can place initial meaningful constraints on the HMF.

Euclid and J-PAS can achieve constraints comparable to simulations.

Independent cluster mass measurements significantly improve HMF determination.

Abstract

The abundances of dark matter halos in the universe are described by the halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behavior through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of type Ia supernovae. Our results show that DES is capable of putting the first meaningful constraints on the HMF, while both Euclid and J-PAS can give stronger constraints, comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even more important for measuring the HMF than for constraining the cosmological parameters, and can vastly improve the determination of the halo mass function. Measuring the HMF could thus be used to cross-check simulations and their implementation of baryon physics. It could even, if deviations cannot be accounted for, hint at new physics.