Measurement of the Polarization of the Cosmic Microwave Background with BICEP3 and the Keck Array Telescopes

Download or read book Measurement of the Polarization of the Cosmic Microwave Background with BICEP3 and the Keck Array Telescopes written by Jae Hwan Kang and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Cosmic Microwave Background (CMB) shows the afterglow image of the Big Bang, providing a window to probe the very early Universe. The CMB encodes the information in the temperature and polarization fluctuations. BICEP3 and the Keck Array telescopes are small aperture refracting telescopes at the South Pole to measure the B-mode polarization of the CMB at the degree angular scales, which holds a key to probe inflation theory. This dissertation presents the progress of the BICEP/Keck Array telescopes on measuring the B modes and the recent test of low elevation observation with BICEP3 to expand its sky coverage at the South Pole. The BICEP/Keck Array telescopes produced the tightest constraint to the power of primordial B-modes, parameterized by the tensor-to-scalar ratio, r, to be less than 0.07 at 95% confidence with the one sigma uncertainty in r about 0.02, using polarization data up to 2015 observing season. BICEP3 was fully deployed for 2016 observing season and has been operating since. Together with the Keck Array telescopes operating at higher frequencies, we expect to achieve the one sigma uncertainty in r about 0.01 from data up to 2018 observing season. During the austral summer of 2018-19, we tested the feasibility of using BICEP3 to observe the CMB at a low elevation at the South Pole. Due to operational constraints, we had to use a flat mirror to direct the beams to the low elevation range. We obtained additional data at the end of the 2019 winter observing season. We present the temperature and polarization maps from this data set, which clearly shows the detection of the E mode polarization. This potentially opens an opportunity to cover an extended patch of the sky at the South Pole. If the primordial B-mode is detected at the main observing field, probing larger areas will reduce sample variance. Larger observing field is also important to study the non-Gaussianity and decorrelation of the foregrounds. An interesting patch in this extended region is the CMB Cold Spot, whose origin is still in question. The possibility of testing polarization anomaly deviating from the standard Gaussian fluctuation around the Cold Spot is discussed.