  We present a new estimate of foreground emission in the WMAP data, using a
Markov chain Monte Carlo (MCMC) method. The new technique delivers maps of each
foreground component for a variety of foreground models, error estimates of the
uncertainty of each foreground component, and provides an overall
goodness-of-fit measurement. The resulting foreground maps are in broad
agreement with those from previous techniques used both within the
collaboration and by other authors.
  We find that for WMAP data, a simple model with power-law synchrotron,
free-free, and thermal dust components fits 90% of the sky with a reduced
chi-squared of 1.14. However, the model does not work well inside the Galactic
plane. The addition of either synchrotron steepening or a modified spinning
dust model improves the fit. This component may account for up to 14% of the
total flux at Ka-band (33 GHz). We find no evidence for foreground
contamination of the CMB temperature map in the 85% of the sky used for
cosmological analysis.

Astrophysics