  Observations by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite
have identified an excess of microwave emission from the centre of the Milky
Way. It has been suggested that this WMAP haze emission could potentially be
synchrotron emission from relativistic electrons and positrons produced in the
annihilations of one (or more) species of dark matter particles. In this paper
we re-calculate the intensity and morphology of the WMAP haze using a
multi-linear regression involving full-sky templates of the dominant forms of
galactic foreground emission, using two different CMB sky signal estimators.
The first estimator is a posterior mean CMB map, marginalized over a general
foreground model using a Gibbs sampling technique, and the other is the ILC map
produced by the WMAP team. Earlier analyses of the WMAP haze used the ILC map,
which is more contaminated by galactic foregrounds than the Gibbs map. In
either case, we re-confirm earlier results that a statistically significant
residual emission remains after foreground subtraction that is concentrated
around the galactic centre. However, we find that the significance of this
emission can be significantly reduced by allowing for a subtle spatial
variation in the frequency dependence of soft synchrotron emission in the inner
and outer parts of the galaxy. We also re-investigate the prospect of a
neutralino dark matter interpretation of the origin of the haze, and find that
significant boosting in the dark matter annihilation rate is required, relative
to that obtained with a smooth galactic dark matter distribution, in order to
reproduce the inferred residual emission, contrary to that deduced in several
recent studies.
