Primordial Non-Gaussianity and Dark Energy Constraints from Cluster Surveys

Galaxy cluster surveys will be a powerful probe of dark energy. At the same time, cluster abundance is sensitive to any non-Gaussianity of the primordial density field. It is therefore possible that non-Gaussian initial conditions might be misinterpreted as a sign of dark energy or at least degrade the expected constraints on dark energy parameters. To address this issue, we perform a likelihood analysis of an ideal cluster survey similar in size and depth to the upcoming South Pole Telescope survey and Dark Energy Survey. We analyze a model in which the strength of the non-Gaussianity is parameterized by the constant f_NL; this model has been used extensively to derive cosmic microwave background (CMB) anisotropy constraints on non-Gaussianity, allowing us to make contact with those works. We find that the constraining power of the cluster survey on dark energy observables is not significantly diminished by non-Gaussianity, provided that cluster redshift information is included in the analysis. We also find that even an ideal cluster survey is unlikely to significantly improve current and future CMB constraints on non-Gaussianity. However, when all systematics are under control, such surveys could constitute a valuable cross-check on CMB observations.