Revisiting WMAP Data Reveals Significant Changes in CMB Power Spectrum

[nicksauce]

This is interesting: http://arxiv.org/abs/0907.2731 ... Apparently there could have been a systematic error in the WMAP temperature maps.

The cosmic microwave background (CMB) temperature maps published by the Wilkinson Microwave Anisotropy Probe (WMAP) team are found to be inconsistent with the differential time-ordered data (TOD), from which the maps are reconstructed. The inconsistency indicates that there is a serious problem in the map making routine of the WMAP team, and it is necessary to reprocess the WMAP data. We develop a self-consistent software package of map-making and power spectrum estimation independently of the WMAP team. Our software passes a variety of tests. New CMB maps are then reconstructed, which are significantly different with the official WMAP maps. In the new maps, the inconsistency disappeared, along with the hitherto unexplained high level alignment between the CMB quadrupole and octopole components detected in released WMAP maps. An improved CMB cross-power spectrum is then derived from the new maps which better agrees with that of BOOMRANG. Two important results are hence obtained: the CMB quadrupole drops to nearly zero, and the power in multiple moment range between 200 and 675 decreases on average by about 13%, causing the best-fit cosmological parameters to change considerably, e.g., the total matter density increases from 0.26 up to 0.32 and the dark energy density decreases from 0.74 down to 0.68. These new parameters match with improved accuracy those of other independent experiments. Our results indicate that there is still room for significant revision in the cosmological model parameters.

 

[Chalnoth]

Well, I was looking over this with a friend last week, and we generally agree: the paper is very light on details, not well-written, and generally lacking in overall rigor. It leaves the impression that they didn't put enough work into the research to really show what they claim to show.

And the thing that worries me is that I'm pretty sure that a number of independent groups have done map making on the WMAP timelines, and it seems rather unlikely to me that they all would have made the same mistake (this paper claims that the error isn't in the algorithm, as they claim to replicate the WMAP team's mapmaking algorithm, but rather in the implementation).