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Measurement of the Polarization of the Cosmic Microwave Background with the BICEP2 and Keck Array Telescopes


Teply, Grant Paul (2015) Measurement of the Polarization of the Cosmic Microwave Background with the BICEP2 and Keck Array Telescopes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9XP72WM.


Precision polarimetry of the cosmic microwave background (CMB) has become a mainstay of observational cosmology. The ΛCDM model predicts a polarization of the CMB at the level of a few μK, with a characteristic E-mode pattern. On small angular scales, a B-mode pattern arises from the gravitational lensing of E-mode power by the large scale structure of the universe. Inflationary gravitational waves (IGW) may be a source of B-mode power on large angular scales, and their relative contribution to primordial fluctuations is parameterized by a tensor-to-scalar ratio r. BICEP2 and Keck Array are a pair of CMB polarimeters at the South Pole designed and built for optimal sensitivity to the primordial B-mode peak around multipole l ~ 100. The BICEP2/Keck Array program intends to achieve a sensitivity to r ≥ 0.02. Auxiliary science goals include the study of gravitational lensing of E-mode into B-mode signal at medium angular scales and a high precision survey of Galactic polarization. These goals require low noise and tight control of systematics. We describe the design and calibration of the instrument. We also describe the analysis of the first three years of science data. BICEP2 observes a significant B-mode signal at 150 GHz in excess of the level predicted by the lensed-ΛCDM model, and Keck Array confirms the excess signal at > 5σ. We combine the maps from the two experiments to produce 150 GHz Q and U maps which have a depth of 57 nK deg (3.4 μK arcmin) over an effective area of 400 deg2 for an equivalent survey weight of 248000 μK2. We also show preliminary Keck Array 95 GHz maps. A joint analysis with the Planck collaboration reveals that much of BICEP2/Keck Array's observed 150 GHz signal at low l is more likely a Galactic dust foreground than a measurement of r. Marginalizing over dust and r, lensing B-modes are detected at 7.0σ significance.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:cosmic background radiation; cosmology: observations; gravitational waves; inflation; instrumentation: polarimeters; telescopes
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Bock, James J.
Group:Astronomy Department
Thesis Committee:
  • Bock, James J. (chair)
  • Golwala, Sunil
  • Spiropulu, Maria
  • Doré, Olivier P.
Defense Date:8 May 2015
Record Number:CaltechTHESIS:06012015-163200704
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8958
Deposited By: Grant Teply
Deposited On:04 Jun 2015 22:56
Last Modified:26 Oct 2021 17:13

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