Abstract
We have described briefly the population of compact sources appearing at CMB frequencies, and studied their non-Gaussianity using publicly available full-sky simulations. Introducing a parametrization permitting to visualise efficiently the bispectrum, we have described the configuration and scale dependence of the bispectrum of radio and IR point sources, as well as its frequency dependence, and shown that it is well fitted by an analytical prescription. We have shown further that the clustering of IR sources increases their non-Gaussianity by several orders of magnitude, and that their bispectrum peaks in the squeezed triangles. Examining the impact of these sources on primordial non-Gaussianity estimation, we have found that the radio sources yield an important positive bias to local fNL estimation at low frequencies, but this bias is efficiently reduced by masking detectable sources. On the other hand, IR sources produce a negative bias at high frequencies, which is not dimmed by the masking, as their clustering is dominated by faint sources.
Highlights
The Cosmic Microwave Background (CMB), the dominant signal on the sky around 100 GHz, is a powerful probe of the early universe which significantly contributes to the establishment of the standard model of cosmology
In the 30350 GHz frequency range, other signals contribute at small angular scales and modify the statistical distribution of the measured CMB anisotropies
Three of these signals are associated with extragalactic sources: - galaxy clusters, in which the electrons of the hot ionised gas scatter off the CMB photons leaving a distinct spectral signature (Sunyaev-Zeldovich effect) - radio loud galaxies with Active Galactic Nuclei emitting through synchrotron and free-free processes - dusty star-forming galaxies, where the UV emission from stars heats the dust which reemits in the infrared domain
Summary
1. Introduction The CMB, the dominant signal on the sky around 100 GHz, is a powerful probe of the early universe which significantly contributes to the establishment of the standard model of cosmology. In the 30350 GHz frequency range, other signals contribute at small angular scales and modify the statistical distribution (initially close to Gaussian) of the measured CMB anisotropies. Radio sources can be considered randomly distributed on the sky and are modeled as a white-noise entirely described by the sources number counts.
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