Beam profile sensitivity of the WMAP CMB power spectrum
  Using the published WMAP 5-year data, we first show how sensitive the WMAP
power spectra are to the form of the WMAP beam. It is well known that the beam
profile derived from observations of Jupiter is non-Gaussian and indeed
extends, in the W band for example, well beyond its 12.'6 FWHM core out to more
than 1 degree in radius. This means that even though the core width corresponds
to wavenumber l\approx1800, the form of the beam still significantly affects
the WMAP results even at l\approx200 which is the scale of the first acoustic
peak. The difference between the beam convolved C_l and the final C_l is
\approx70% at the scale of the first peak, rising to \approx400% at the scale
of the second.
  New estimates of the Q, V and W-band beam profiles are then presented, based
on a stacking analysis of the WMAP5 radio source catalogue and temperature
maps. The radio sources show a significantly (3-4\sigma) broader beam profile
on scales of 10'-30' than that found by the WMAP team whose beam analysis is
based on measurements of Jupiter. Beyond these scales the beam profiles from
the radio sources are too noisy to give useful information. Furthermore, we
find tentative evidence for a non-linear relation between WMAP and ATCA/IRAM 95
GHz source fluxes. We discuss whether the wide beam profiles could be caused
either by radio source extension or clustering and find that neither
explanation is likely. We also argue against the possibility that Eddington
bias is affecting our results. The reasons for the difference between the radio
source and the Jupiter beam profiles are therefore still unclear. If the radio
source profiles were then used to define the WMAP beam, there could be a
significant change in the amplitude and position of even the first acoustic
peak. It is therefore important to identify the reasons for the differences
between these two beam profile estimates.
