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Published April 1, 2009 | Published
Journal Article Open

High-Resolution CMB Power Spectrum from the Complete ACBAR Data Set


In this paper, we present results from the complete set of cosmic microwave background (CMB) radiation temperature anisotropy observations made with the Arcminute Cosmology Bolometer Array Receiver (ACBAR) operating at 150 GHz. We include new data from the final 2005 observing season, expanding the number of detector hours by 210% and the sky coverage by 490% over that used for the previous ACBAR release. As a result, the band-power uncertainties have been reduced by more than a factor of two on angular scales encompassing the third to fifth acoustic peaks as well as the damping tail of the CMB power spectrum. The calibration uncertainty has been reduced from 6% to 2.1% in temperature through a direct comparison of the CMB anisotropy measured by ACBAR with that of the dipole-calibrated WMAP5 experiment. The measured power spectrum is consistent with a spatially flat, ΛCDM cosmological model. We include the effects of weak lensing in the power spectrum model computations and find that this significantly improves the fits of the models to the combined ACBAR+WMAP5 power spectrum. The preferred strength of the lensing is consistent with theoretical expectations. On fine angular scales, there is weak evidence (1.1σ) for excess power above the level expected from primary anisotropies. We expect any excess power to be dominated by the combination of emission from dusty protogalaxies and the Sunyaev-Zel'dovich effect (SZE). However, the excess observed by ACBAR is significantly smaller than the excess power at ℓ > 2000 reported by the CBI experiment operating at 30 GHz. Therefore, while it is unlikely that the CBI excess has a primordial origin; the combined ACBAR and CBI results are consistent with the source of the CBI excess being either the SZE or radio source contamination.

Additional Information

© 2009 The American Astronomical Society. Received 2008 January 12; accepted 2008 November 9; published 2009 March 24. The ACBAR program has been primarily supported by NSF office of polar programs grants OPP-8920223 and OPP-0091840. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098. Some computations were performed on the Canada Foundation for Innovation funded CITA Sunnyvale cluster. Chao-Lin Kuo acknowledges support from a NASA postdoctoral fellowship, and Marcus Runyan acknowledges support from a Fermi fellowship. Christian Reichardt acknowledges support from a National Science Foundation Graduate Research Fellowship. Some of the results in this paper have been derived using the HEALPix (Gorski et al. 2005) package. We thank members of the BOOMERANG team, in particular Brendan Crill, Bill Jones, and Tom Montroy for providing access to the B03 data, the pipeline used to generate simulation maps, and assistance with its operation. We thank Antony Lewis for discussions about ways to parameterize tests for weak lensing in the data.

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Published - Reichardt2009p1366Astrophys_J.pdf


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