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Published March 10, 2010 | Published
Journal Article Open

Measurement of Cosmic Microwave Background Polarization Power Spectra from Two Years of BICEP Data


Background Imaging of Cosmic Extragalactic Polarization (BICEP) is a bolometric polarimeter designed to measure the inflationary B-mode polarization of the cosmic microwave background (CMB) at degree angular scales. During three seasons of observing at the South Pole (2006 through 2008), BICEP mapped ~2% of the sky chosen to be uniquely clean of polarized foreground emission. Here, we present initial results derived from a subset of the data acquired during the first two years. We present maps of temperature, Stokes Q and U, E and B modes, and associated angular power spectra. We demonstrate that the polarization data are self-consistent by performing a series of jackknife tests. We study potential systematic errors in detail and show that they are sub-dominant to the statistical errors. We measure the E-mode angular power spectrum with high precision at 21 ≤ ℓ ≤ 335, detecting for the first time the peak expected at ℓ ~ 140. The measured E-mode spectrum is consistent with expectations from a ΛCDM model, and the B-mode spectrum is consistent with zero. The tensor-to-scalar ratio derived from the B-mode spectrum is r = 0.02^(+0.31)_(–0.26), or r < 0.72 at 95% confidence, the first meaningful constraint on the inflationary gravitational wave background to come directly from CMB B-mode polarization.

Additional Information

© 2010 American Astronomical Society. Issue 2 (2010 March 10); received 2009 June 15; accepted for publication 2010 January 29; published 2010 February 22. We dedicate this work to the memory of Andrew Lange, whose tragic and untimely death has deeply pained us all. He was and always will be an inspiration to us, and he is immeasurably missed. Bicep is supported by NSF Grant No. OPP-0230438, Caltech President's Discovery Fund, Caltech President's Fund PF-471, JPL Research and Technology Development Fund, and the late J. Robinson. We thank the South Pole Station staff for helping make our observing seasons a success. We also thank Joanna Dunkley, Nathan Miller, and our colleagues in Acbar, Boomerang, QUaD, Bolocam, SPT, and WMAP for advice and helpful discussions, and Kathy Deniston for logistical and administrative support. We gratefully acknowledge support of individual team members by the NASA Graduate Fellowship program (H.C.C.), NSF PECASE Award No. AST-0548262 (B.G.K.), the John B. and Nelly Kilroy Foundation (J.M.K.), the U.S. DOE contract to SLAC No. DE-AC02-76SF00515 (C.L.K. and J.E.T.), KICP (C.P. and C.S.), and the NASA Science Mission Directorate via the US Planck Project (G.R.).

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