Wilkinson Microwave Anisotropy Probe
Processing, intensity and Polarization Exclusion Masks
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 Bennett, et.al., 2013. 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 majority of sources in the intensity masks, with the exception that a radius of 1.2 degrees is used for point sources brighter than 5 Jy in any of the WMAP bands. An exclusion radius of 1.0 degrees is used 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_kq85") corresponds roughly to the "Kp2" cut in the 3-year data release; the extended cut ("temperature_kq75") 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 9-year point source catalogs. The region outside of this mask consists of pixels that are either outside of the diffuse component of the nine-year KQ85 temperature analysis mask or outside of the seven-year point source catalog mask.
Year 2 required special handing to avoid extremely low N-Obs in K-band near Jupiter; for year 2 the number of masked pixels were reduced to allow those K maps to achieve convergence.