Implications of multiple high-redshift galaxy clusters

To date, 14 high-redshift (z>1.0) galaxy clusters with mass measurements have been observed, spectroscopically confirmed, and are reported in the literature. These objects should be exceedingly rare in the standard {Lambda} cold dark matter ({Lambda}CDM) model. We conservatively approximate the selection functions of these clusters' parent surveys and quantify the tension between the abundances of massive clusters as predicted by the standard {Lambda}CDM model and the observed ones. We alleviate the tension, considering non-Gaussian primordial perturbations of the local type, characterized by the parameter f{sub NL}, and derive constraints on f{sub NL} arising from the mere existence of these clusters. At the 95% confidence level, f{sub NL}>467, with cosmological parameters fixed to their most likely WMAP5 values, or f{sub NL} > or approx. 123 (at 95% confidence) if we marginalize over prior WMAP5 parameters. In combination with f{sub NL} constraints from cosmic microwave background and halo bias, this determination implies a scale dependence of f{sub NL} at {approx_equal}3{sigma}. Given the assumptions made in the analysis, we expect any future improvements to the modeling of the non-Gaussian mass function, survey volumes, or selection functions to increase the significance of f{sub NL}>0 found here. In order to reconcile these massive, high-z clustersmore » with f{sub NL}=0, their masses would need to be systematically lowered by 1.5{sigma}, or the {sigma}{sub 8} parameter should be {approx}3{sigma} higher than cosmic microwave background (and large-scale structure) constraints. The existence of these objects is a puzzle: it either represents a challenge to the {Lambda}CDM paradigm or it is an indication that the mass estimates of clusters are dramatically more uncertain than we think.« less