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Published December 1, 2012 | Published
Journal Article Open

Second Season QUIET Observations: Measurements of the Cosmic Microwave Background Polarization Power Spectrum at 95 GHz


The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 μK√s. Four low-foreground fields were observed, covering a total of ~1000 deg^2 with an effective angular resolution of 12'.8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C_ℓ (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between ℓ = 25 and 975 and find that the EE spectrum is consistent with ΛCDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1^(+0.9)_(–0.8) (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2^(+0.9)_(–0.8) (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

Additional Information

© 2012 American Astronomical Society. Received 2012 July 20; accepted 2012 September 23; published 2012 November 16. Support for the QUIET instrument and operation comes through the NSF cooperative agreement AST-0506648. Support was also provided by NSF awards PHY-0355328, AST-0448909, PHY-0551142, PHY-0855887, and AST-1010016; KAKENHI 20244041, 20740158, and 21111002; PRODEX C90284; a KIPAC Enterprise grant; and by the Strategic Alliance for the Implementation of New Technologies (SAINT). Some work was performed on the Joint Fermilab-KICP Supercomputing Cluster, supported by grants from Fermilab, the Kavli Institute for Cosmological Physics, and the University of Chicago. Some work was performed on the Titan Cluster, owned and maintained by the University of Oslo and NOTUR (the Norwegian High Performance Computing Consortium), and on the Central Computing System, owned and operated by the Computing Research Center at KEK. 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-AC02-05CH11231. Portions of this work were performed at the Jet Propulsion Laboratory (JPL) and California Institute of Technology, operating under a contract with the National Aeronautics and Space Administration. The Q-band modules were developed using funding from the JPL R&TD program. We acknowledge the Northrop Grumman Corporation for collaboration in the development and fabrication of HEMT-based cryogenic temperature-compatible MMICs. We acknowledge the use of the Planck Sky Model, developed by the Component Separation Working Group (WG2) of the Planck Collaboration. Some of the results in this paper have been derived using the HEALPix (Gorski et al. 2005) software and analysis package. C.D. acknowledges an STFC Advanced Fellowship and an ERC IRG grant under FP7. R.B. acknowledges support from CONICYT project Basal PFB-06 and ALMA-Conicyt 31070015. A.D.M. acknowledges a Sloan foundation fellowship. H.K.E. acknowledges an ERC Starting Grant under FP7. PWV measurements were provided by the Atacama Pathfinder Experiment (APEX). We thank CONICYT for granting permission to operate within the Chajnantor Scientific Preserve in Chile, and ALMA for providing site infrastructure support. Field operations were based at the Don Esteban facility run by Astro-Norte. We are particularly indebted to the engineers and technician who maintained and operated the telescope: José Cortés, Cristobal Jara, Freddy Muñoz, and Carlos Verdugo. In addition, we acknowledge the following people for their assistance in the instrument design, construction, commissioning, operation, and in data analysis: Augusto Gutierrez Aitken, Colin Baines, Phil Bannister, Hannah Barker, Matthew R. Becker, Alex Blein, Mircea Bogdan, Anushya Chandra, Sea Moon Cho, Joelle Cooperrider, Mike Crofts, Emma Curry, Maire Daly, Richard Davis, Fritz Dejongh, Joy Didier, Greg Dooley, Hans Eide, Pedro Ferreira, Jonathon Goh, Will Grainger, Peter Hamlington, Takeo Higuchi, Seth Hillbrand, Christian Holler, Ben Hooberman, Kathryn D. Huff, William Imbriale, Oliver King, Eiichiro Komatsu, Jostein Kristiansen, Richard Lai,David Leibovitch, Erik Leitch, Kelly Lepo, Siqi Li, Martha Malin, Mark McCulloch, Steve Meyer, Oliver Montes, David Moore, Ian O'Dwyer, Gustavo Orellana, Stephen Osborne, Heather Owen, Stephen Padin, Felipe Pedreros, Ashley Perko, Alan Robinson, Jacklyn Sanders, Dale Sanford, Yunior Savon, Mary Soria, Alex Sugarbaker, David Sutton, Matias Vidal, Liza Volkova, Edward Wollack, Stephanie Xenos, Octavio Zapata, Mark Zaskowski, and Joseph Zuntz.

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