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Directional Dependence of ΛCDM Cosmological Parameters

Axelsson, M. and Fantaye, Y. and Hansen, F. K. and Banday, A. J. and Eriksen, H. K. and Gorski, K. M. (2013) Directional Dependence of ΛCDM Cosmological Parameters. Astrophysical Journal Letters, 773 (1). Art. No. L3. ISSN 2041-8205. doi:10.1088/2041-8205/773/1/L3.

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We study hemispherical power asymmetry in the Wilkinson Microwave Anisotropy Probe 9 yr data. We analyze the combined V- and W-band sky maps, after application of the KQ85 mask, and find that the asymmetry is statistically significant at the 3.4σ confidence level for ℓ = 2-600, where the data are signal-dominated, with a preferred asymmetry direction (l, b) = (227, –27). Individual asymmetry axes estimated from six independent multipole ranges are all consistent with this direction. Subsequently, we estimate cosmological parameters on different parts of the sky and show that the parameters A_s, n_s , and Ω_b are the most sensitive to this power asymmetry. In particular, for the two opposite hemispheres aligned with the preferred asymmetry axis, we find n_s = 0.959 ± 0.022 and n_s = 0.989 ± 0.024, respectively.

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Additional Information:© 2013 American Astronomical Society. Received 2013 March 22; accepted 2013 June 27; published 2013 July 24. F.K.H. acknowledges OYI grant from the Norwegian research council. H.K.E. acknowledges support through the ERC Starting Grant StG2010-257080. We acknowledge the use of resources from the Norwegian national super computing facilities NOTUR. Maps and results have been derived using the HEALpix ( software package developed by Górski et al. (2005). Results have been derived using the CosmoMC code from Lewis & Bridle (2002). We acknowledge the use of the LAMBDA archive (Legacy Archive for Microwave Background Data Analysis). Support for LAMBDA is provided by the NASA office for Space Science.
Funding AgencyGrant Number
Norwegian research council OYI grantUNSPECIFIED
ERC Starting GrantStG2010-257080
NASA Office of Space ScienceUNSPECIFIED
Subject Keywords:cosmic background radiation; cosmology: observations; methods: statistical
Issue or Number:1
Record Number:CaltechAUTHORS:20130918-113501429
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Official Citation:Directional Dependence of ΛCDM Cosmological Parameters M. Axelsson et al. 2013 ApJ 773 L3
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41387
Deposited On:18 Sep 2013 20:39
Last Modified:10 Nov 2021 04:29

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