Estimating f_NL and g_NL from Massive High-Redshift Galaxy Clusters

TL;DR

This paper revisits the estimation of non-Gaussianity parameters from high-redshift galaxy clusters, correcting previous methodological issues and providing updated constraints on f_NL and g_NL consistent with cosmological observations.

Contribution

It identifies and remedies methodological problems in estimating non-Gaussianity from galaxy clusters, refining constraints on f_NL and exploring the role of g_NL in explaining cluster abundance.

Findings

Previous f_NL values are unphysically small.

For WMAP cosmology, f_NL > 411 at 95% confidence.

g_NL > 2*10^6 could explain cluster abundance and voids.

Abstract

There are observations of 15 high-redshift massive galaxy clusters, which have an extremely small probability with a purely Gaussian initial curvature perturbation. Here we revisit the estimation of the contribution of non-Gaussianities to the cluster mass function and point out serious problems that have resulted in the application of the mass function out of the range of its validity. We remedy the situation and show that the values of f_NL previously claimed to completely reconcile (i.e. at ~100% confidence) the existence of the clusters with LambdaCDM are unphysically small. However, for WMAP cosmology and at 95% confidence, we arrive at the limit f_NL>411, which is similar to previous estimates. We also explore the possibility of a large g_NL as the reason for the observed excess of the massive galaxy clusters. This scenario, g_NL>2*10^6, appears to be in more agreement with CMB and LSS limits for the non-Gaussianity parameters and could also provide an explanation for the overabundance of large voids in the early universe.