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CLASSE NEWS | 28 May 2014

First Results from the Atacama Cosmology Telescope Polarimeter Announced

Measurements of the cosmic microwave background (CMB) provide the foundation for modern cosmology: the study of the universe as a whole. Current CMB surveys extend beyond previous measurements by mapping the CMB temperature and polarization with better sensitivity and at smaller angular scales. There is a great deal of excitement surrounding recent CMB polarization measurements, which may provide information about the inflationary expansion that is believed to have occurred in the first millionth of a trillionth of a trillionth of a second after the big bang. Cornell’s experimental cosmology research group (including Prof. Michael Niemack, Dr. Francesco De Bernardis, Dr. Shawn Henderson, Brian Koopman, and Patricio Gallardo) recently announced the best measurements of the parity-symmetric (aka. “E-mode”) polarization on small angular scales. These measurements were made using the first 3-months of data from the Atacama Cosmology Telescope Polarimeter (ACTPol) with only one third of the ACTPol instrument installed. The data are consistent with the dark energy and cold dark matter dominated cosmological model and demonstrate the remarkable sensitivity of ACTPol. The ACTPol team is working on completing the ACTPol upgrade, which will enable measurements of the parity-antisymmetric (aka. “B-mode”) polarization that could lead to a better understanding of inflation in the early universe. Robust measurements of the “B-mode” polarization signal from inflation (if it exists) will probe physics at grand unification energy scales, a trillion times higher energy than is probed at the Large Hadron Collider. A copy of the preprint describing these exciting new results can be found here.

Example maps of one region of the sky observed by ACTPol made from data taken in the 2013 season. The six panels show (left to right, top to bottom) maps of the intensity ("T") of the Cosmic Microwave Background and its polarization (which can be fully specified by measurements of either the pairs "Q" and "U" or "E" and "B"). In particular, the bottom left image is a zoom of the indicated portion of the upper left intensity map, with a point source circled (a quasar candidate) and a cluster of galaxies circled, the latter measured indirectly through its Suyaev-Zel'dovich (SZ) distortion of the CMB.