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Journal-club Univers / Journal-club Universe

« Foreground-immune CMB lensing with shear-only reconstruction »

Emmanuel Schaan
Dept. Astron., Univ. California (Berkeley, California, Etats-Unis d'Amérique)

CMB lensing from upcoming experiments such as AdvACT, SPT-3G and Simons Observatory relies primarily on temperature, rather than polarization. In this regime, foreground contamination to the temperature maps produces significant lensing biases, which cannot be fully controlled by multi-frequency component separation, masking or bias hardening.
In this presentation, I will split the standard quadratic estimator into a shear and magnification estimators (Bucher et al 2010, Prince et al 2017). After computing the foreground biases from simulations, I will show that the shear estimator is insensitive to foregrounds, even when applied to a single-frequency temperature map contaminated with CIB, tSZ, kSZ and radio point sources.
By dramatically reducing the foreground biases, the shear estimator allows us to increase the maximum temperature multipole included, beyond what would normally be possible for the standard quadratic estimator, thus increasing the overall statistical power of CMB lensing measurements. In addition, the magnification estimator is extremely sensitive to foregrounds, and therefore provides a useful diagnostic for potential residual foregrounds.
jeudi 3 mai 2018 - 14:00
Salle 281, Institut d'Astrophysique
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