Measurement of cosmic microwave background polarization power spectra from two years of bicep data

H. C. Chiang, P. A R Ade, D. Barkats, J. O. Battle, E. M. Bierman, J. J. Bock, C. D. Dowell, L. Duband, E. F. Hivon, W. L. Holzapfel, V. V. Hristov, W. C. Jones, B. G. Keating, J. M. Kovac, C. L. Kuo, A. E. Lange, E. M. Leitch, P. V. Mason, T. Matsumura, H. T. NguyenN. Ponthieu, C. Pryke, S. Richter, G. Rocha, C. Sheehy, Y. D. Takahashi, J. E. Tolan, K. W. Yoon

Research output: Contribution to journalArticlepeer-review

214 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1123-1140
Number of pages18
JournalAstrophysical Journal
Issue number2
StatePublished - 2010


  • Cosmic background radiation
  • Cosmology: observations
  • Gravitational waves
  • Inflation
  • Polarization


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