Pseudo-dipole signal removal from WMAP data

Liu, Hao; Li, Ti-Pei

doi:10.1007/s11434-010-4222-0

Cited by 13 publications

(11 citation statements)

References 21 publications

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“…2). 4 This strongly questions the validity of the WMAP result, and indicates that most of the released WMAP CMB quadrupole might be artificial because of the timing asynchronism effect, as demonstrated by Roukema (2010b); Liu et al (2010); Liu & Li (2011a) and this work.…”

Section: Consequence Of the Timing Offsetmentioning

confidence: 75%

“…Besides the detected timing offset, other observational factors, e.g. the sidelobe pickup contamination from dipole, can also generate artificial quadrupoles aligned with what is observed in the official CMB map and which need to be further removed by model fitting (Liu & Li 2011a,b). After template‐based removal of artificial quadrupole, the remaining quadrupole power can be as low as 10.4 μK 2 , significantly lower than the 28.6 μK 2 value derived in this work, indicating that the sidelobe‐pickup‐induced artifact cannot be ignored.…”

Section: Discussionmentioning

confidence: 99%

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Diagnosing timing error in WMAP data

Liu¹,

Xiong²,

Li³

2011

Monthly Notices of the Royal Astronomical Society: Letters

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The Doppler dipole signal dominates the cosmic microwave background (CMB) anisotropy maps obtained by the Wilkinson Microwave Anisotropy Probe (WMAP) mission, and plays a key role throughout the data processing. Previously, we discovered a timing asynchronism of −25.6 ms between the timestamps of the spacecraft attitude and radiometer output in the original raw WMAP time‐ordered data (TOD), which, if not corrected during data processing, would generate an artificial quadrupole component (l= 2) in recovered CMB maps (Liu, Xiong & Li 2010). Recently, Roukema (2010b) proves that there does exist a timing offset‐induced error corresponding to about −25.6 ms in the WMAP calibrated TOD, by studying the fluctuation variance per pixel in the temperature map recovered from the TOD as a function of assumed timing offset. Here, we find evidence directly in the WMAP TOD for such an uncorrected timing error, which possibly occurred in calculating the Doppler dipole signal during the WMAP team's TOD data processing. The amplitude is highly significant and is consistent with previous work. We also show that the uncorrected timing offset can lead the WMAP CMB quadrupole to be substantially overestimated.

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Section: Consequence Of the Timing Offsetmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Diagnosing timing error in WMAP data

Liu¹,

Xiong²,

Li³

2011

Monthly Notices of the Royal Astronomical Society: Letters

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“…The previously published results are now thought of as being questionable and perhaps even unfortunate artifacts of primitive data analyses [27,28]. More clever analysis by others now suggest rather, that the CMB is really very smooth, without many of the features presented in [25,26] and in reality the CMB signal is nearly flawless [29,30]. The well-considered analysis of the CMB data by Liu and Li is consistent with a highly isotropic and homogeneous Universe from singularity up to recombination.…”

Section: Introductionmentioning

confidence: 79%

Is the possible fine-structure constant drift also a test of a time-dependent Planck constant?

Öztaş

Smith

2011

Sci. China Phys. Mech. Astron.

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The recent publication of spatial and distance variation of the fine-structure constant, α, derived from astronomical data of quasar emissions (QE) is exciting. The decreasing value of α over time, derived from data obtained from the Very Large Telescope (VLT) in Chile, encourages the search for other possible running constants. We surmise that emissions from distant supernovae, type Ia (SNe Ia), which are more blue than predictions are best explained by a decreasing Planck constant with increasing lookback time. We present some results from our theoretical work and comparison to the astronomical observations and suggest that both α and h might be running constants. More data are required to answer several questions about the origin of the "drifting" α and the possible time dependence of h. Astronomical tools such as SNe and QE may be the best means to secure the exacting data needed to confirm or deny these hypotheses. alpha, quasars, distance measurement, supernovae, CMB

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“…Secondly, in calculating T d with Eq. 1, the effect of overall sidelobe response uncertainty of radio telescope can equivalently introduce an error in the direction vector n, which is estimated to be ∼ 10 ′ −20 ′ for WMAP (Liu & Li 2011a). Furthermore, an undocumented 25.6 ms timing offset error in WMAP time-ordered-data (TOD) has been revealed (Liu, Xiong & Li 2011;Roukema 2010), which also can deviate calculated dipole signals as an antenna pointing direction error of ∼ 7 ′ does .…”

Section: Introductionmentioning

confidence: 99%

Missing completely of the CMB quadrupole in WMAP data

Liu

2013

Chin. Sci. Bull.

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In cosmic microwave background (CMB) experiments, foreground-cleaned temperature maps are still contaminated by the residual dipole due to uncertainties of the Doppler dipole direction and microwave radiometer sidelobe. To obtain reliable CMB maps, such contamination has to be carefully removed from observed data. We have previously built a software package for map-making, residual dipole-contamination removal, and power spectrum estimation from the Wilkinson Microwave Anisotropy Probe (WMAP) raw data. This software has now been significantly improved. With the improved software, we obtain a negative result of CMB quadrupole detection with the WMAP raw data, which is −3.2 ± 3.5 µK 2 from the seven-year WMAP (WMAP7) data. This result is evidently incompatible with ∼ 1000 µK 2 expected from the standard cosmological model ΛCDM. The completely missing of CMB quadrupole poses a serious challenge to the standard model and sets a strong constraint on possible models of cosmology. Due to the importance of this result for understanding the origin and early evolution of our universe, the software codes we used are opened for public checking.

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Pseudo-dipole signal removal from WMAP data

Cited by 13 publications

References 21 publications

Diagnosing timing error in WMAP data

Diagnosing timing error in WMAP data

Is the possible fine-structure constant drift also a test of a time-dependent Planck constant?

Missing completely of the CMB quadrupole in WMAP data

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