Forecasts on the contamination induced by unresolved point sources in primordial non-Gaussianity beyond Planck

Abstract

In this paper we present forecasts of the contamination on different shapes of the primordial non-Gaussianity fnl parameter – detectable on future cosmic microwave background (CMB) high-resolution anisotropy maps – produced by unresolved extragalactic point sources at frequencies of cosmological interest (45–375 GHz). We consider two scenarios: an ideal (noiseless) mission and a possible future space-borne satellite, with instrumental characteristics similar to the ones proposed for the Cosmic Origins Explorer (COrE). The local, equilateral, orthogonal and flat shapes are considered in both temperature (intensity) and polarized emission data. The angular power spectrum and bispectrum of extragalactic point sources are estimated by state-of-the-art models of source number counts. The impact of all the most relevant (far-infrared and radio selected) source populations on these shapes at COrE frequencies is studied. The results of this analysis show that unresolved extragalactic point sources should not induce a very relevant non-Gaussian signal in the frequency range 100–200 GHz, thus not preventing a correct estimate of the CMB primordial fnl parameter. Polarization information allows one to significantly reduce the error-bars in the fnl parameter and the bias induced by unresolved sources and, hence, to widen the range of frequencies for fnl studies. On the contrary, at ν < 100 GHz or ν > 225 GHz, important non-Gaussian deviations in CMB anisotropy maps are expected due to unresolved extragalactic sources.