Implications for Primordial Non-Gaussianity (f_NL) from weak lensing masses of high-z galaxy clusters

TL;DR

This paper explores how deviations from Gaussian initial conditions in the early universe could explain the observed abundance of a high-redshift galaxy cluster, providing a new way to probe primordial non-Gaussianity.

Contribution

It demonstrates that non-Gaussianity with f_NL in the range 150-200 can significantly increase the probability of observing such massive clusters at high redshift.

Findings

Non-Gaussianity can boost cluster abundance by factors > 3-10.

The required f_NL range is comparable to CMB constraints.

Massive high-z clusters can serve as probes of primordial non-Gaussianity.

Abstract

The recent weak lensing measurement of the dark matter mass of the high-redshift galaxy cluster XMMUJ2235.3-2557 of (8.5 +- 1.7) x 10^{14} Msun at z=1.4, indicates that, if the cluster is assumed to be the result of the collapse of dark matter in a primordial gaussian field in the standard LCDM model, then its abundance should be < 0.002 clusters in the observed area. Here we investigate how to boost the probability of XMMUJ2235.3-2557 in particular resorting to deviations from Gaussian initial conditions. We show that this abundance can be boosted by factors > 3-10 if the non-Gaussianity parameter f^local_NL is in the range 150-200. This value is comparable to the limit for f_NL obtained by current constraints from the CMB. We conclude that mass determination of high-redshift, massive clusters can offer a complementary probe of primordial non-gaussianity.