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

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.