| Abstract |
The spectral variation of the cosmic microwave background (CMB) as
observed by WMAP was tested using foreground reduced WMAP5 data, by
producing subtraction maps at the 1° angular resolution between the
two cosmological bands of V and W, for masked sky areas that avoid the
Galactic disk. The resulting V - W map revealed a non-acoustic
signal over and above the WMAP5 pixel noise, with two main properties.
First, it possesses quadrupole power at the ≈1 μK level which may
be attributed to foreground residuals. Second, it fluctuates also at all
values of ell> 2, especially on the 1° scale (200 lsim ell lsim
300). The behavior is random and symmetrical about zero temperature with
an rms ≈7 μK, or 10% of the maximum CMB anisotropy, which would
require a "cosmic conspiracy" among the foreground components if it is a
consequence of their existence. Both anomalies must be properly
diagnosed and corrected if "precision" cosmology is the claim. The
second anomaly is, however, more interesting because it opens the
question on whether the CMB anisotropy genuinely represents primordial
density seeds. |