The mass-concentration relationship of virialized halos and its impact on cosmological observables

TL;DR

This paper examines how different mass-concentration relationships of virialized halos influence cosmological measurements, highlighting the sensitivity of lensing peak counts to these relationships and assessing baryonic physics effects.

Contribution

It compares various published mass-concentration relations and evaluates their impact on cosmological observables, especially lensing peak counts, in the context of upcoming surveys.

Findings

Lensing peak counts are highly sensitive to the mass-concentration relationship.

Disparities in reported mass-concentration fits exceed uncertainties from sigma-8.

Baryonic physics likely does not explain high concentrations in some clusters.

Abstract

A generic property of the cuspy simulated virialized halos in cold dark matter cosmogenies is that their concentration is inversely correlated with their mass. This behavior has also been confirmed in observations, although differences in the exact form and dispersion of this so-called mass-concentration relationship have been reported. Some observational studies of massive halos suggest that they are statistically over-concentrated with respect to the expectations of Lambda-CDM. Here we investigate the impact that various published mass-concentration relationships, both from simulations and derived from observations, would have on other cosmological observables, in particular considering upcoming surveys. We find that an integral measure of lensing shear, such as counts of peaks from halos, is very sensitive to the relationship between mass and concentration at fixed sigma-8, and the disparity between some reported fits is much larger than the impact of uncertainty in sigma-8 itself. We also briefly assess the impact of baryonic physics on cluster scale observables, using state-of-the-art simulations, concluding that it is unlikely to give rise to the high concentrations reported for some clusters.