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[0907.2731] Improved CMB Map from WMAP Data
Authors:Hao Liu, Ti-Pei Li
Abstract: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.
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Adam Amara

Joined: 25 Sep 2004
Posts: 18
Affiliation: ETH

PostPosted: July 17 2009  Reply with quote

I just noticed this reanalysis of the WMAP data. I don't know a lot about the pipelines for CMB data. Does anyone have thoughts about this?


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Dragan Huterer

Joined: 18 Jul 2005
Posts: 24
Affiliation: University of Michigan

PostPosted: July 23 2009  Reply with quote

Yes, this is interesting, but I couldn't figure out exactly what is different between their analysis of the TOD and WMAP's.

The only thing that was clearly mentioned was that they didn't use data from when the beam is within 7 degrees from outer planets, while WMAP allegedly excluded only within 1.5 degrees. Is that the only difference?!
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Boud Roukema

Joined: 24 Feb 2005
Posts: 84
Affiliation: Torun Centre for Astronomy, University of Nicolaus Copernicus

PostPosted: March 16 2010  Reply with quote

Dragan Huterer wrote:
Yes, this is interesting, but I couldn't figure out exactly what is different between their analysis of the TOD and WMAP's

With hindsight, that may turn out to be the most important result
from Liu & Li 0907.2731: they tried to
analyse the TOD in the same, presumably correct, way that the WMAP
team did, this successfully passed most tests and gave nearly identical
results - except that the quadrupole weakened by half an order of
magnitude. They didn't know why, and suggested that it would be cool
if the WMAP team could help find the difference.

The WMAP team presumably failed to "spot the difference" during the following
seven months, but Liu & Li found it. They also found an elegant way of producing
the supposedly cosmological quadrupole using spacecraft attitude history and no CMB temperature
maps, since the former is where they unintentionally had done something
differently to the WMAP team.

Anyway, that thread is at:
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Joe Whitbourn

Joined: 28 Jul 2010
Posts: 2
Affiliation: Durham University

PostPosted: July 28 2010  Reply with quote

The quadrupole that Lui and Li report for the reprocessed WMAP5 maps, [37.3, 24.4(safe-mode)] μK2 is small compared to official released WMAP figure of 108.7 μK2

But it's not that small compared to the distribution of quadrupoles in a /\CDM universe. The WMAP team in their recent paper on anomalies (1001.4758) found a range of [40,3200] μK2

Not that this is relevant to the authors idea that the quadrupole isn't cosmological but is an instrument artifact, as argued in 1003.1073.
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