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Galactic foreground contributions to the 5-year Wilkinson Microwave Anisotropy Probe maps

Macellari, N. and Pierpaoli, E. and Dickinson, C. and Vaillancourt, J. E. (2011) Galactic foreground contributions to the 5-year Wilkinson Microwave Anisotropy Probe maps. Monthly Notices of the Royal Astronomical Society, 418 (2). pp. 888-905. ISSN 0035-8711.

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We compute the cross-correlation between intensity and polarization from the 5-year Wilkinson Microwave Anisotropy Probe (WMAP5) data in different sky regions with respect to template maps for synchrotron, dust and free–free emission. We derive the frequency dependence and polarization fraction for all three components in 48 different sky regions of HEALPix (N_(side)= 2) pixelization. The anomalous emission associated with dust is clearly detected in intensity over the entire sky at the K (23-GHz) and Ka (33-GHz) WMAP bands, and is found to be the dominant foreground at low Galactic latitudes, between b =−40° and +10°. The synchrotron spectral index obtained from the K and Ka WMAP bands from an all-sky analysis is β_s=−3.32 ± 0.12 for intensity and β_s=−3.01 ± 0.03 for polarized intensity. The polarization fraction of the synchrotron emission is constant in frequency and increases with latitude from ≈5 per cent near the Galactic plane up to ≈40 per cent in some regions at high latitudes; the average value for |b| < 20° is 8.6 ± 1.7 (stat) ± 0.5 (sys) per cent, while for |b| > 20°, it is 19.3 ± 0.8 (stat) ± 0.5 (sys) per cent. Anomalous dust and free–free emissions appear to be relatively unpolarized. Monte Carlo simulations showed that there were biases of the method due to cross-talk between the components, at up to ≈5 per cent in any given pixel, and ≈1.5 per cent on average, when the true polarization fraction is low (a few per cent or less). Nevertheless, the average polarization fraction of dust-correlated emission at the K band is 3.2 ± 0.9 (stat) ± 1.5 (sys) per cent or less than 5 per cent at 95 per cent confidence. When comparing real data with simulations, eight regions show a detected polarization above the 99th percentile of the distribution from simulations with no input foreground polarization, six of which are detected at above 2σ and display polarization fractions between 2.6 and 7.2 per cent, except for one anomalous region, which has 32 ± 12 per cent. The dust polarization values are consistent with the expectation from spinning dust emission, but polarized dust emission from magnetic-dipole radiation cannot be ruled out. Free–free emission was found to be unpolarized with an upper limit of 3.4 per cent at 95 per cent confidence.

Item Type:Article
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URLURL TypeDescription DOIArticle
Pierpaoli, E.0000-0002-7957-8993
Dickinson, C.0000-0002-0045-442X
Additional Information:© 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS. Accepted 2011 July 28. Received 2011 July 12; in original form 2009 December 23. Article first published online: 18 Oct 2011. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration and funded through the Director’s Research and Development Fund Program. EP is an NSF-ADVANCE fellow (AST 06-49899) also supported by NASA grant NNX07AH59G and Planck subcontract 1290790.NM and EP were supported by JPL SURP award 1314616 for this work, and would like to thank Caltech for hospitality during this period. EP wishes to thank the Aspen Center for Physics where part of this work was carried out. CD acknowledges an STFC Advanced Fellowship and ERC grant under the FP7. JEV is supported by NSF AST 05-40882 and 08-38261 through the Caltech Submillimeter Observatory. The authors would like to thank Mark Halpern and Anthony Banday for useful conversations.We acknowledge the use of the LAMBDA. Support for the LAMBDA is provided by the NASA Office of Space Science. Some of the results in this paper have been derived using the HEALPIX (Gόrski et al. 2005) package.
Funding AgencyGrant Number
NSFAST 06-49899
Aspen Center for PhysicsUNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
European Research Council (ERC)UNSPECIFIED
NSFAST 05-40882
Caltech Submillimeter Observatory08-38261
Subject Keywords: polarization; ISM: general; Galaxy: general; cosmic background radiation; diffuse radiation; radio continuum: ISM
Issue or Number:2
Record Number:CaltechAUTHORS:20120221-150835631
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Official Citation:Macellari, N., Pierpaoli, E., Dickinson, C. and Vaillancourt, J. E. (2011), Galactic foreground contributions to the 5-year Wilkinson Microwave Anisotropy Probe maps. Monthly Notices of the Royal Astronomical Society, 418: 888–905. doi: 10.1111/j.1365-2966.2011.19542.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29397
Deposited By: Ruth Sustaita
Deposited On:21 Feb 2012 23:47
Last Modified:18 Nov 2020 23:57

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