Constraints on non-Gaussianity from Sunyaev-Zeldovich cluster surveys

Abstract

We perform a Fisher matrix analysis to forecast the capability of ongoing and future Sunyaev-Zeldovich cluster surveys in constraining the deviations from Gaussian distribution of primordial density perturbations. We use the constraining power of the cluster number counts and clustering properties to forecast limits on the ${f}_{\mathrm{NL}}$ parameter. The primordial non-Gaussianity (NG) effects on the mass function and halo bias are considered. We adopt self-calibration for the mass-observable scaling relation and evaluate constraints for the South Pole Telescope, Planck, CCAT-like, South Pole Telescope polarization survey, and Atacama Cosmology Telescope polarization survey. We show that the scale dependence of the halo bias induced by the local NG provides strong constraints on ${f}_{\mathrm{NL}}$, while the results from number count are two orders of magnitude worse. When combining information from number counts and the power spectrum, the Planck cluster catalog provides the tightest constraint with ${\ensuremath{\sigma}}_{{f}_{\mathrm{NL}}}=7$ (68% C.L.) even for relatively conservative assumptions on the expected cluster yields and systematics. This value is a factor of 2 smaller than the $1\ensuremath{\sigma}$ error as measured by WMAP cosmic microwave background measurements and comparable to what is expected from Planck. We find that the results are mildly sensitive to the mass threshold of the surveys but strongly depend on the survey coverage; a full-sky survey like Planck is more favorable because it can probe longer wavelength modes that are most sensitive to NG effects. In addition, the constraints are largely insensitive to priors on nuisance parameters as they are mainly driven by the power spectrum probe, which has a mild dependence on the mass-observable relations.