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Published May 10, 2007 | Published
Journal Article Open

Implications of the Cosmic Background Imager Polarization Data


We present new measurements of the power spectra of the E mode of cosmic microwave background (CMB) polarization, the temperature T, the cross-correlation of E and T, and upper limits on the B mode from 2.5 yr of dedicated Cosmic Background Imager (CBI) observations. Both raw maps and optimal signal images in the (u, v)-plane and the sky plane show strong detections of the E mode (11.7 σ for the EE power spectrum overall) and no detection of the B mode. The power spectra are used to constrain parameters of the flat tilted adiabatic ΛCDM models: those determined from EE and TE bandpowers agree with those from TT, which is a powerful consistency check. There is little tolerance for shifting polarization peaks from the TT-forecast locations, as measured by the angular sound crossing scale θ = 100/l_s = 1.03 ± 0.02 from EE and TE; compare with 1.044 ± 0.005 with the TT data included. The scope for extra out-of-phase peaks from subdominant isocurvature modes is also curtailed. The EE and TE measurements of CBI, DASI, and BOOMERANG are mutually consistent and, taken together rather than singly, give enhanced leverage for these tests.

Additional Information

© 2007 The American Astronomical Society. Received 2005 October 12; accepted 2006 October 26. We are indebted to the DASI team of the Kavli Institute for Cosmological Physics at the University of Chicago, led by John Carlstrom, and especially to John Kovac, who designed the achromatic polarizers. We thank the Kavli Operating Institute, Barbara and Stanley Rawn, Jr., Maxine and Ronald Linde, Cecil and Sally Drinkward, Rochus Vogt, and the Provost, President, and PMA Division Chairman of the California Institute of Technology for their generous support. We gratefully acknowledge support from the Canadian Institute for Advanced Research, the Canadian Space Agency, and NSERC at CITA. This research used the MacKenzie cluster at CITA, funded by the Canada Foundation for Innovation. This work was supported by the National Science Foundation under grants AST 94-13935, AST 98-02989, AST 00-98734, and AST 02-06416. R. B. was supported partially by CONICYT. L. B. and J.M. acknowledge support from the Chilean Center for Astrophysics FONDAP grant 15010003, and S. T. acknowledges support from grant Milenio ICMP02-049. This work was supported by the Leverhulme Trust and PPARC at Oxford. A. C. T. acknowledges support from the Royal Society. We thank CONICYT for granting permission to operate within the Chanjnantor Scientific Preserve in Chile, and the National Radio Astronomy Observatory (NRAO) Central Development Lab for developing the HEMT amplifiers used in this project and assisting with production. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank Jo Dunkley, Carrie MacTavish, and Mike Nolta for helpful comments. We thank Wilson Araya and Jose´ Cortes for their dedicated work in operating the CBI.

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