A New Limit on CMB Circular Polarization from SPIDER
We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of SPIDER, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very sm...
Published in: | The Astrophysical Journal |
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Main Authors: | , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
American Astronomical Society
2017
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Subjects: | |
Online Access: | https://authors.library.caltech.edu/79749/ https://authors.library.caltech.edu/79749/1/Nagy_2017_ApJ_844_151.pdf https://authors.library.caltech.edu/79749/2/1704.00215.pdf https://resolver.caltech.edu/CaltechAUTHORS:20170802-102243947 |
Summary: | We present a new upper limit on cosmic microwave background (CMB) circular polarization from the 2015 flight of SPIDER, a balloon-borne telescope designed to search for B-mode linear polarization from cosmic inflation. Although the level of circular polarization in the CMB is predicted to be very small, experimental limits provide a valuable test of the underlying models. By exploiting the nonzero circular-to-linear polarization coupling of the half-wave plate polarization modulators, data from SPIDER's 2015 Antarctic flight provide a constraint on Stokes V at 95 and 150 GHz in the range 33 < ℓ < 307. No other limits exist over this full range of angular scales, and SPIDER improves on the previous limit by several orders of magnitude, providing 95% C.L. constraints on ℓ(ℓ + 1)C^(VV)_ ℓ/(2π) ranging from 141 to 255 μK^2 at 150 GHz for a thermal CMB spectrum. As linear CMB polarization experiments become increasingly sensitive, the techniques described in this paper can be applied to obtain even stronger constraints on circular polarization. |
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