University of Cambridge > > Cosmology Lunch > The CIB-lensing bispectrum: impact on primordial non-Gaussianity and detectability for the Planck mission

The CIB-lensing bispectrum: impact on primordial non-Gaussianity and detectability for the Planck mission

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If you have a question about this talk, please contact Tommaso Giannantonio.

I will characterise the bispectrum generated by the interplay between the cosmic infrared background (CIB) radiation and the gravitational lensing effect, the CIB -lensing bispectrum. This bispectrum can correlate and bias the primordial non-Gaussianity CMB bispectrum measured with the Planck anisotropy maps. I will review the non-primordial contributions to the CMB bispectrum that we have already considered in the Planck 2015 Results. I will show that the CIB -lensing bispectrum has a considerable strength and that it can be detected with high significance in the Planck high-frequency maps. I will also present forecasts of the contamination on different shapes of the primordial non- Gaussianity fnl parameter produced by the CIB -lensing bispectrum and by the extragalactic point sources bispectrum in the Planck high-resolution CMB anisotropy maps. The local, equilateral and orthogonal shapes are considered for ‘raw’ single-frequency (i.e. without applying any component separation technique) and foreground-reduced Planck temperature maps. The CIB -lensing correlation mainly affects orthogonal shapes of the bispectrum at the 143 and 217 GHz bands, respectively – while point sources mostly impact equilateral shapes at 100, 143 and 217 GHz. However, the results indicate that these contaminants do not induce any relevant bias on Planck fnl estimates when foregroundreduced maps are considered. Using SEVEM for the component separation, we obtain a maximum bias of 0.30σ and 0.45σ for the orthogonal and equilateral shapes respectively. This component separation technique is, in fact, able to partially clean the extragalactic source contamination and the bias is reduced for all the shapes. We have further developed single and multiple-frequency estimators based on the Komatsu, Spergel & Wandelt formalism.

This talk is part of the Cosmology Lunch series.

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