Two-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: A Measurement of Circular Polarization at 40 GHz
Date
2020-02-01Author
Padilla, Ivan L.
Eimer, Joseph R.
Li, Yunyang
Addison, Graeme E.
Ali, Aamir
Appel, John W.
Bennett, Charles L.
Bustos Placencia, Ricardo
Brewer, Michael K.
Chan, Manwei
Chuss, David T.
Cleary, Joseph
Couto, Jullianna Denes
Dahal, Sumit
Denis, Kevin
Dünner, Rolando
Essinger-Hileman, Thomas
Fluxá, Pedro
Gothe, Dominik
Haridas, Saianeesh K.
Harrington, Kathleen
Iuliano, Jeffrey
Karakla, John
Marriage, Tobias A.
Miller, Nathan J.
Núñez, Carolina
Parker, Lucas
Petroff, Matthew A.
Reeves, Rodrigo
Rostem, Karwan
Stevens, Robert W.
Nunes Valle, Deniz Augusto
Watts, Duncan J.
Weiland, Janet L.
Wollack, Edward J.
Xu, Zhilei
Publisher
Astrophysical JournalDescription
Metadata
Show full item recordAbstract
We report measurements of circular polarization from the first two years of observation with the 40 GHz
polarimeter of the Cosmology Large Angular Scale Surveyor (CLASS). CLASS is conducting a multi-frequency
survey covering 75% of the sky from the Atacama Desert designed to measure the cosmic microwave background
(CMB) linear E and B polarization on angular scales 1° θ 90°, corresponding to a multipole range of
2 ℓ 200. The modulation technology enabling measurements of linear polarization at the largest angular
scales from the ground, the Variable-delay Polarization Modulator, is uniquely designed to provide explicit
sensitivity to circular polarization (Stokes V ). We present a first detection of circularly polarized atmospheric
emission at 40 GHz that is well described by a dipole with an amplitude of 124 4 K m when observed at an
elevation of 45°, and discuss its potential impact on the recovery of linear polarization by CLASS. Filtering the
atmospheric component, CLASS places a 95% confidence upper limit of 0.4 Km 2 to 13.5 Km 2 on
ℓℓ C ( ) () + 1 2 ℓ p VV for 1 120 ℓ , representing an improvement by two orders of magnitude over previous
CMB limits.