First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Emission

The WMAP mission has mapped the full sky to determine the geometry, content, and evolution of the universe. Full sky maps are made in five microwave frequency bands to separate the temperature anisotropy of the cosmic microwave background (CMB) from foreground emission, including diffuse Galactic emission and Galactic and extragalactic point sources. We define masks that excise regions of high foreground emission, so CMB analyses can be carried out with minimal foreground contamination. We also present maps and spectra of the individual emission components, leading to an improved understanding of Galactic astrophysical processes. The effectiveness of template fits to remove foreground emission from the WMAP data is also examined. These efforts result in a CMB map with minimal contamination and a demonstration that the WMAP CMB power spectrum is insensitive to residual foreground emission. We use a Maximum Entropy Method to construct a model of the Galactic emission components. The observed total Galactic emission matches the model to <1% and the individual model components are accurate to a few percent. We find that the Milky Way resembles other normal spiral galaxies between 408 MHz and 23 GHz, with a synchrotron spectral index that is flattest (βs ∼ −2.5) near star-forming regions, especially in the plane, and steepest (βs ∼ −3) in the halo. This is consistent with a picture of relativistic cosmic ray electron generation in star-forming regions and diffusion and convection within the plane. The significant synchrotron index steepening out of the plane suggests a diffusion process in which the halo electrons are WMAP is the result of a partnership between Princeton University and NASA’s Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team. Code 685, Goddard Space Flight Center, Greenbelt, MD 20771 Science Systems and Applications, Inc. (SSAI), 10210 Greenbelt Road, Suite 600 Lanham, Maryland 20706 Dept. of Physics, Jadwin Hall, Princeton, NJ 08544 Dept of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 UCLA Astronomy, PO Box 951562, Los Angeles, CA 90095-1562 Dept. of Physics and Astronomy, University of British Columbia, Vancouver, BC Canada V6T 1Z1 National Research Council (NRC) Fellow Depts. of Astrophysics and Physics, EFI and CfCP, University of Chicago, Chicago, IL 60637 Dept. of Physics, Brown University, Providence, RI 02912

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