Detection of B-Mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope

• Published in: Physical Review Letters
• Main Authors: Hanson, D., Bock, J. J., Padin, S., Schulz, B., Vieira, J. D., Viero, M. P., Zemcov, M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Physical Society 2013
• Subjects: Curl; South Pole; South pole
• Online Access: https://authors.library.caltech.edu/42272/; https://authors.library.caltech.edu/42272/1/PhysRevLett.111.141301.pdf; https://authors.library.caltech.edu/42272/7/1307.5830v2.pdf; https://resolver.caltech.edu/CaltechAUTHORS:20131106-111142604

Gravitational lensing of the cosmic microwave background generates a curl pattern in the observed polarization. This “B-mode” signal provides a measure of the projected mass distribution over the entire observable Universe and also acts as a contaminant for the measurement of primordial gravity-wave signals. In this Letter we present the first detection of gravitational lensing B modes, using first-season data from the polarization-sensitive receiver on the South Pole Telescope (SPTpol). We construct a template for the lensing B-mode signal by combining E-mode polarization measured by SPTpol with estimates of the lensing potential from a Herschel-SPIRE map of the cosmic infrared background. We compare this template to the B modes measured directly by SPTpol, finding a nonzero correlation at 7.7σ significance. The correlation has an amplitude and scale dependence consistent with theoretical expectations, is robust with respect to analysis choices, and constitutes the first measurement of a powerful cosmological observable.