Papers › The Atacama Cosmology Telescope: Constraints on Cosmic Birefringence
The Atacama Cosmology Telescope: Constraints on Cosmic Birefringence
Toshiya Namikawa, Yilun Guan, Omar Darwish, Blake D. Sherwin, Simone Aiola, Nicholas Battaglia, James A. Beall, Daniel T. Becker, J. Richard Bond, Erminia Calabrese, Grace E. Chesmore, Steve K. Choi, Mark J. Devlin, Joanna Dunkley, Rolando Dünner, Anna E. Fox, Patricio A. Gallardo, Vera Gluscevic, Dongwon Han, Matthew Hasselfield, Gene C. Hilton, Adam D. Hincks, Renée Hložek, Johannes Hubmayr, Kevin Huffenberger, John P. Hughes, Brian J. Koopman, Arthur Kosowsky, Thibaut Louis, Marius Lungu, Amanda MacInnis, Mathew S. Madhavacheril, Maya Mallaby-Kay, Loïc Maurin, Jeffrey McMahon, Kavilan Moodley, Sigurd Naess, Federico Nati, Laura B. Newburgh, John P. Nibarger, Michael D. Niemack, Lyman A. Page, Frank J. Qu, Naomi Robertson, Alessandro Schillaci, Neelima Sehgal, Cristóbal Sifón, Sara M. Simon, David N. Spergel, Suzanne T. Staggs, Emilie R. Storer, Alexander van Engelen, Jeff van Lanen, Edward J. Wollack
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We present new constraints on anisotropic birefringence of the cosmic microwave background polarization using two seasons of data from the Atacama Cosmology Telescope covering 456 square degrees of sky. The birefringence power spectrum, measured using a curved-sky quadratic estimator, is consistent with zero. Our results provide the tightest current constraint on birefringence over a range of angular scales between 5 arcminutes and 9 degrees. We improve previous upper limits on the amplitude of a scale-invariant birefringence power spectrum by a factor of between 2 and 3. Assuming a nearly-massless axion field during inflation, our result is equivalent to a 2 σ upper limit on the Chern-Simons coupling constant between axions and photons of g_(αγ)<4.0×10⁻²/H_I where H_I is the inflationary Hubble scale.
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