A new limit on CMB circular polarization from SPIDER

• Published in: The Astrophysical Journal
• Main Authors: Nagy, J. M., Ade, Peter, Amiri, M., Benton, S. J., Bergman, A. S., Bihary, R., Bock, J. J., Bond, J. R., Bryan, S. A., Chiang, H. C., Contaldi, C. R., Doré, O., Duivenvoorden, A. J., Eriksen, H. K., Farhang, M., Filippini, J. P., Fissel, L. M., Fraisse, A. A., Freese, K., Galloway, M., Gambrel, A. E., Gandilo, N. N., Ganga, K., Gudmundsson, J. E., Halpern, M., Hartley, J., Hasselfield, M., Hilton, G., Holmes, W., Hristov, V. V., Huang, Z., Irwin, K. D., Jones, W. C., Kuo, C. L., Kermish, Z. D., Li, S., Mason, P. V., Megerian, K., Moncelsi, L., Morford, T. A., Netterfield, C. B., Nolta, M., Padilla, I. L., Racine, B., Rahlin, A. S., Reintsema, C., Ruhl, J. E., Runyan, M. C., Ruud, T. M., Shariff, J. A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Astronomical Society 2017
• Subjects: QB Astronomy; QC Physics; Antarctic; Antarc*
• Online Access: https://orca.cardiff.ac.uk/id/eprint/104199/; https://doi.org/10.3847/1538-4357/aa7cfd; https://orca.cardiff.ac.uk/id/eprint/104199/1/A%20New%20Limit%20on%20CMB%20Circular%20Polarization%20from%20SPIDER.pdf

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 $33\lt {\ell }\lt 307$. 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 ${\ell }({\ell }+1){C}_{{\ell }}^{{VV}}/(2\pi )$ ranging from 141 to 255 μK2 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.