Wilkinson Microwave Anisotropy Probe

The data made available through this page has been updated. The most recent version of this data may be accessed through /product/map/current/

Product Name
Intensity and Polarization Exclusion Masks
Coord. System
Projection Type
HEALPix, nested


A number of WMAP data analysis applications use pixel masks to exclude foreground-contaminated portions of the sky from the analysis. Diffuse emission in Stokes I (temperature) is masked using a combination of cuts in the K band and Q band maps, as described in Gold et al. Diffuse emission in Stokes Q and U is masked using cuts in K band polarized intensity combined with a model of thermal dust emission. Point sources are masked based on a combination of external catalog data and WMAP-detected sources. The source exclusion radius is 0.6 degree for the intensity masks and 1.0 degrees for all but one source in the polarization masks. The exception is Cen A, which is masked to a radius of 3 degrees in polarization.

Mask values for each map pixel are provided in the N_obs field of the data file (the 'Temperature' field should be disregarded). A mask value of zero means the pixel is rejected; a value of one means the pixel is accepted. For temperature analysis, we provide two cut levels: the standard cut ("temperature_analysis") corresponds roughly to the "Kp2" cut in the 3-year data release; the extended cut ("extended temperature analysis") corresponds roughly to the "Kp0" cut in the 3-year data release. For all the analysis and processing masks we provide the data at multiple pixel resolutions. For all but the polarization analysis mask, the cut is defined at the lowest supplied resolution and all higher resolution versions mask the same sky area. The polarization analysis mask is defined at Nside=512 (r9) but we also provide a degraded version at Nside=16 (r4) for low-l analysis. For this mask, an r4 pixel is included (set to one) if more than 50% of its daughter r9 pixels are set to one.

The point source catalog mask was used to exclude Galactic plane and Magellanic cloud regions in making the WMAP 5-year point source catalog. For the Magellanic clouds, pixels within a 6 degree radius of l=280.46, b=-32.89 and a 4 degree radius of l=302.80, b=-44.31 are masked. For the Galactic plane, the Kp0 intensity mask from the 1-year and 3-year analyses was used with a minor change. Isolated mask regions with fewer than 500 contiguous HEALPix res 9 pixels are no longer included in the mask. Except for this change, the 5-year point source catalog mask is the same as that used for the 1-year and 3-year catalogs.

Mask Sky Fraction
Admitted (%)
wmap_temperature_analysis_mask_r9_5yr_v3.fits 82 512 Temperature analysis/KQ85 mask
wmap_temperature_analysis_mask_r10_5yr_v3.fits 82 1024 Temperature analysis/KQ85 mask
wmap_ext_temperature_analysis_mask_r9_5yr_v3.fits 72 512 Extended temperature analysis/KQ75 mask
wmap_polarization_analysis_mask_r4_5yr_v3.fits 73 16 Polarization analysis mask
wmap_polarization_analysis_mask_r9_5yr_v3.fits 73 512 Polarization analysis mask
wmap_processing_mask_r4_5yr_v3.fits 94 16 Processing mask
wmap_processing_mask_r8_5yr_v3.fits 94 256 Processing mask
wmap_processing_mask_r9_5yr_v3.fits 94 512 Processing mask
wmap_processing_mask_r10_5yr_v3.fits 94 1024 Processing mask
wmap_point_source_catalog_mask_r9_5yr_v3.fits 78 512 Point source catalog mask
wmap_temperature_source_mask_r9_5yr_v3.fits 97 512 Temperature point source mask

Additional Information

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A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
Web Curator: Mr. Michael R. Greason