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
MCMC Foreground Maps
Coord. System
Projection Type
HEALPix, nested, res 6 (Nside=64)


These maps were generated from the MCMC fit described in Gold, et.al.. The inputs are the one degree smoothed maps per frequency band, binned to Nside=64. There is an MCMC chain for each pixel which is used to estimate the likelihood for all the parameters. The maps provided for each parameter are:

  • The best-fit parameter (i.e. peak likelihood) from each chain.
  • The mean parameter over the chain.
  • The marginalized variance.

Three sets of maps are provided: a "base" model, a shifted spinning dust model, and a steepening synchrotron model. Each model has a slightly different set of parameters that are allowed to vary.

The following parameters are allowed to vary when performing the fit at each pixel:

Parameter Notes
Synchrotron temperature at K-band All three models.
Free-free temperature at K-band All three models.
Dust temperature at W-band All three models.
Synchrotron spectral index Base and steepening synchrotron models only. Fixed to -3.0 in the shifted spinning dust model.
Dust spectral index Base model only; fixed to +2.0 in the other two models.
CMB temperature Thermodynamic units. All three models.
Synchrotron Stokes Q at K-band All three models.
Dust Stokes Q at W-band All three models.
CMB Stokes Q Thermodynamic units. All three models.
CMB Stokes U Thermodynamic units. All three models.
Spinning Dust Temperature at K-band Shifted spinning dust model only.
Synchrotron Steepening Parameter Steepening synchrotron model only.
Error flags. All three models. Each pixel is bit-coded:
  • 0 - no error
  • 1 - did not find a good adaptive stepsize in the "prechain" for that pixel, but the chain was run anyway
  • 2 - the chain for that pixel failed the convergence test
  • 4 - not used
  • 8 - not used
  • 16 - pixel was masked before processing, no fit was done
Best fit reduced χ2 All three models.

Parameters Derived from Stokes Q using K-band Polarization Directions

Synchrotron Stokes U at K-band All three models.
Dust Stokes U at W-band All three models.

Temperatures in mK are in antenna units except for the CMB maps, which are provided in thermodymanic units.

The reduced χ2 are the best-fit χ2 divided by the number of degrees of freedom determined from the chain using the "effective complexity".

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