Gravity Group Lunch Seminar, Colin Hill | IAS/CCA "Extragalactic Foreground Biases in Primordial non-Gaussianity Measurements from the CMB"

Fri, Apr 19, 2019, 12:00 pm

Abstract: The cosmic microwave background (CMB) temperature bispectrum is currently the most precise tool for constraining non-Gaussianity (NG) in the primordial curvature perturbations.  The Planck temperature data tightly constrain the amplitude of local-type NG, as could be generated in (e.g.) multi-field inflation: f_NL^loc = 2.5 +/- 5.7.  However, all analyses to date have neglected to explicitly assess several biases on f_NL due to extragalactic foregrounds in CMB temperature maps.  In this talk, I will present a complete calculation of all such biases on local-type NG estimates, as well as potentially important contributions to estimators for other shapes of primordial NG.  Most of the biases are non-blackbody in nature, and are thus reduced by multifrequency component separation methods; however, recent analyses have found that extragalactic foregrounds are present at non-negligible levels in the Planck component-separated maps.  For Planck, some of the biases are comparable to the statistical error bar on f_NL; for future experiments, they can greatly exceed the statistical errors (considering temperature data only), and will thus require careful treatment.

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Location: 
102 Jadwin Hall