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/
Foreground Reduced Sky Maps Per Frequency Band
HEALPix, nested, res 9 (Nside=512)
0.23°- 0.93° (frequency dependent)
The foreground reduced skymaps were produced by removing a foreground model from the 'unreduced' maps using the Foreground Template Model discussed in Hinshaw, et.al., 2006 and Page, et.al, 2006; see those papers for details. Briefly, synchrotron, free-free, and dust emission templates were modeled and then subtracted from the single year 'unreduced' maps. The goal was to produce a set of maps with the foreground removed while retaining WMAP's noise characteristics.
Because the K and Ka maps were used to produce the foreground models, only Q, V, and W band foreground reduced maps were created and delivered to LAMBDA.
As with the 'unreduced' maps, full three year maps were produced by performing a weighted, pixel-by-pixel, mean of the three single year maps; the N_Obs measurement was used to weight this mean. The N_Obs measurements were added together to produce the final, three year, N_Obs measurement.
This same weighted mean method was then used to combine three year maps of the same frequency band into a single map for each frequency. Two maps were combined to produce the Q and V band maps; four maps were combined to produce the W band map.
WMAP maps are stored in FITS binary table extensions. The maps are stored in the first extension in a file; the format of this table depends upon whether polarization maps have been included in the file. Some files also contain the polarization covariance matrices for the maps; if supplied these matrices are stored in a second binary table extension.
As previously stated, the first FITS extension contains the maps. These maps
are in a nested HEALPix format, with
each row representing a single pixel. There are either four or two columns
depending upon whether or not polarization maps are included; these columns
The column names were selected to be compatible with existing HEALPix software. The TEMPERATURE and N_OBS columns are the only columns that exist in files that do not contain polarization maps.