Year: 2008
Type: article
Abstract: In this paper we analyze the biasing effect of point sources, either thermal Sunyaev-Zeldovich clusters or standard radio sources, on the estimated strength of the non-Gaussianity in the cosmic microwave background (CMB). We show that the biggest contribution comes from the cross correlation of the CMB with the matter density rather than from the Poisson term which is conventionally assumed in these calculations. For the three year WMAP data, we estimate that point sources could produce a non-Gaussian signature equivalent to a bias in ${f}_{NL}$ of 0.35, 0.24, $\ensuremath{-}0.097$, $\ensuremath{-}0.13$ in the Ka, Q, V, and W bands, respectively. The level of bias we find is largely insufficient to explain the very high ${f}_{NL}$ values recently detected by Yadav and Wandelt. For Planck, we estimate the point source bispectra to contaminate the ${f}_{NL}$ estimator with a bias of 1.3, 0.34, $\ensuremath{-}0.25$, $\ensuremath{-}0.48$ at 30, 44, 70, 100 GHz, respectively. These results depend on the assumed redshift distribution of the point sources. However, given the projected Planck sensitivity of $\ensuremath{\Delta}{f}_{NL}\ensuremath{\simeq}5$ (95% C.L.), a good estimate of point sources' properties including their number density and redshift distribution is essential before deriving strong conclusions on primordial non-Gaussianity.
Authors: Daniel Babich, Elena Pierpaoli
Institution: California Institute of Technology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W1990992777