In the 5-year WMAP data analysis,a new parametrization form for dark energy equation-of-state was used,and it has been shown that the equation-of-state,w(z),crosses the cosmological-constant boundary w =-1.Based onthi...In the 5-year WMAP data analysis,a new parametrization form for dark energy equation-of-state was used,and it has been shown that the equation-of-state,w(z),crosses the cosmological-constant boundary w =-1.Based onthis observation,in this paper,we investigate the reconstruction of quintom dark energy model.As a single-real-scalarfieldmodel of dark energy,the generalized ghost condensate model provides us with a successful mechanism for realizingthe quintom-like behavior.Therefore,we reconstruct this scalar-field quintom dark energy model from the WMAP 5-yearobservational results.As a comparison,we also discuss the quintom reconstruction based on other specific dark energyansatzs,such as the CPL parametrization and the holographic dark energy scenarios.展开更多
We apply a Cross-Correlation (CC) method developed previously for detecting gamma-ray point sources to the WMAP first year data by using the Point-Spread Function of WMAP and obtain a full sky CC coefficient map. We f...We apply a Cross-Correlation (CC) method developed previously for detecting gamma-ray point sources to the WMAP first year data by using the Point-Spread Function of WMAP and obtain a full sky CC coefficient map. We find that the CC method is a pow- erful tool to examine the WMAP foreground residuals which can be further cleaned accord- ingly. Evident foreground signals are found in the WMAP foreground cleaned maps and the Tegmark cleaned map. In this process 101 point sources are detected, and 26 of them are new sources additional to the originally listed WMAP 208 sources. We estimate the ?ux of these new sources and verify them by another method. As a result, a revised mask file based on the WMAP first year data is produced by including these new sources.展开更多
We investigate large-angle scale temperature anisotropy in the Cosmic Microwave Background (CMB) with the Wilkinson Microwave Anisotropy Probe (WMAP) data and model the large-angle anomalies as the effect of the CMB q...We investigate large-angle scale temperature anisotropy in the Cosmic Microwave Background (CMB) with the Wilkinson Microwave Anisotropy Probe (WMAP) data and model the large-angle anomalies as the effect of the CMB quadrupole anisotropies caused by the local density inhomogeneities. The quadrupole caused by the local density inhomogeneities is different from the special relativity kinematic quadrupole. If the observer inhabits a strong inhomogeneous region, the local quadrupole should not be neglected. We calculate such local quadrupole under the assumption that there is a huge density fluctuation field in the direction (284-, 74-), where the density fluctuation is 10-3 , and its center is ～ 112 h-1 Mpc away from us. After removing such mock signals from WMAP data, the power in the quadrupole, C 2 , increases from the range (200 ～ 260 μK 2 ) to ～ 1000 μK 2 . The quantity S, which is used to estimate the alignment between the quadrupole and the octopole, decreases from (0.7 ～ 0.74) to (0.31 ～ 0.37), while the model predicts that C 2 = 1071.5 μK 2 , and S = 0.412. So our local density inhomogeneity model can, in part, explain the WMAP low-anomalies.展开更多
A remarkable inconsistency between the calibrated differential time-ordered data (TOD) of the Wilkinson Microwave Anisotropy Probe (WMAP) mission,which is the input for map-making,and the cosmic microwave background (...A remarkable inconsistency between the calibrated differential time-ordered data (TOD) of the Wilkinson Microwave Anisotropy Probe (WMAP) mission,which is the input for map-making,and the cosmic microwave background (CMB) temperature maps published by the WMAP team is revealed,indicating that there must exist a serious problem in the map making routine of the WMAP team.This inconsistency is easy to be confirmed without the use of WMAP map-making software.In view of the importance of this issue for cosmology study,we invite readers to check it by themselves.展开更多
We have discovered in our previous work that different observational systematics,e.g.errors from antenna pointing directions or an asynchronism between the attitude and science data may generate a pseudo-dipole signal...We have discovered in our previous work that different observational systematics,e.g.errors from antenna pointing directions or an asynchronism between the attitude and science data may generate a pseudo-dipole signal in the full-sky maps of the cosmic microwave background (CMB) anisotropy that have been published by the Wilkinson Microwave Anisotropy Probe (WMAP) team.We have found that the antenna sidelobe response to the Doppler signal produces a similar effect.In this work,independent from the sources,we have uniformly modeled the pseudo-dipole signal and have removed it from the published WMAP7 CMB maps by model fitting.The result demonstrates that the released WMAP CMB quadrupole is almost completely artificial.展开更多
Recently Background Imaging of Cosmic Extragalactic Polarization(B2)discovered the relic gravitational waves at 7.0σconfidence level.However,the other cosmic microwave background(CMB)data,for example Planck data rele...Recently Background Imaging of Cosmic Extragalactic Polarization(B2)discovered the relic gravitational waves at 7.0σconfidence level.However,the other cosmic microwave background(CMB)data,for example Planck data released in 2013(P13),prefer a much smaller amplitude of the primordial gravitational waves spectrum if a power-law spectrum of adiabatic scalar perturbations is assumed in the six-parameterΛCDM cosmology.In this paper,we explore whether the wCDM model and the running spectral index can relax the tension between B2 and other CMB data.Specifically we found that a positive running of running of spectral index is preferred at 1.7σlevel from the combination of B2,P13 and WMAP Polarization data.展开更多
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 sidelob...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 K2 from the seven-year WMAP (WMAP7) data. This result is evidently incompatible with ～1000 K2 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.展开更多
基金Supported by the Natural Science Foundation of China under Grant Nos.10705041 and 10975032
文摘In the 5-year WMAP data analysis,a new parametrization form for dark energy equation-of-state was used,and it has been shown that the equation-of-state,w(z),crosses the cosmological-constant boundary w =-1.Based onthis observation,in this paper,we investigate the reconstruction of quintom dark energy model.As a single-real-scalarfieldmodel of dark energy,the generalized ghost condensate model provides us with a successful mechanism for realizingthe quintom-like behavior.Therefore,we reconstruct this scalar-field quintom dark energy model from the WMAP 5-yearobservational results.As a comparison,we also discuss the quintom reconstruction based on other specific dark energyansatzs,such as the CPL parametrization and the holographic dark energy scenarios.
基金Supported by the National Natural Science Foundation of China.
文摘We apply a Cross-Correlation (CC) method developed previously for detecting gamma-ray point sources to the WMAP first year data by using the Point-Spread Function of WMAP and obtain a full sky CC coefficient map. We find that the CC method is a pow- erful tool to examine the WMAP foreground residuals which can be further cleaned accord- ingly. Evident foreground signals are found in the WMAP foreground cleaned maps and the Tegmark cleaned map. In this process 101 point sources are detected, and 26 of them are new sources additional to the originally listed WMAP 208 sources. We estimate the ?ux of these new sources and verify them by another method. As a result, a revised mask file based on the WMAP first year data is produced by including these new sources.
文摘We investigate large-angle scale temperature anisotropy in the Cosmic Microwave Background (CMB) with the Wilkinson Microwave Anisotropy Probe (WMAP) data and model the large-angle anomalies as the effect of the CMB quadrupole anisotropies caused by the local density inhomogeneities. The quadrupole caused by the local density inhomogeneities is different from the special relativity kinematic quadrupole. If the observer inhabits a strong inhomogeneous region, the local quadrupole should not be neglected. We calculate such local quadrupole under the assumption that there is a huge density fluctuation field in the direction (284-, 74-), where the density fluctuation is 10-3 , and its center is ～ 112 h-1 Mpc away from us. After removing such mock signals from WMAP data, the power in the quadrupole, C 2 , increases from the range (200 ～ 260 μK 2 ) to ～ 1000 μK 2 . The quantity S, which is used to estimate the alignment between the quadrupole and the octopole, decreases from (0.7 ～ 0.74) to (0.31 ～ 0.37), while the model predicts that C 2 = 1071.5 μK 2 , and S = 0.412. So our local density inhomogeneity model can, in part, explain the WMAP low-anomalies.
基金supported by the National Basic Research Program of China (Grant No.2009CB824800)China Postdoctoral Science Foundation (Grant No.H91I21734A)Knowledge Innovation Program of CAS (Grant No.KJCX2-YW-T03)
文摘A remarkable inconsistency between the calibrated differential time-ordered data (TOD) of the Wilkinson Microwave Anisotropy Probe (WMAP) mission,which is the input for map-making,and the cosmic microwave background (CMB) temperature maps published by the WMAP team is revealed,indicating that there must exist a serious problem in the map making routine of the WMAP team.This inconsistency is easy to be confirmed without the use of WMAP map-making software.In view of the importance of this issue for cosmology study,we invite readers to check it by themselves.
基金supported by the National Natural Science Foundation of China (11033003)National Basic Research Program of China (2009CB824800)the CAS project (KJCX2-YW-T03)
文摘We have discovered in our previous work that different observational systematics,e.g.errors from antenna pointing directions or an asynchronism between the attitude and science data may generate a pseudo-dipole signal in the full-sky maps of the cosmic microwave background (CMB) anisotropy that have been published by the Wilkinson Microwave Anisotropy Probe (WMAP) team.We have found that the antenna sidelobe response to the Doppler signal produces a similar effect.In this work,independent from the sources,we have uniformly modeled the pseudo-dipole signal and have removed it from the published WMAP7 CMB maps by model fitting.The result demonstrates that the released WMAP CMB quadrupole is almost completely artificial.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10821504, 11322545, 11335012, 11173021 and 11322324)the Project of KIP of the Chinese Academy of Sciences and the National Basic Research Program of China (Grant No. 2012CB821804)
文摘Recently Background Imaging of Cosmic Extragalactic Polarization(B2)discovered the relic gravitational waves at 7.0σconfidence level.However,the other cosmic microwave background(CMB)data,for example Planck data released in 2013(P13),prefer a much smaller amplitude of the primordial gravitational waves spectrum if a power-law spectrum of adiabatic scalar perturbations is assumed in the six-parameterΛCDM cosmology.In this paper,we explore whether the wCDM model and the running spectral index can relax the tension between B2 and other CMB data.Specifically we found that a positive running of running of spectral index is preferred at 1.7σlevel from the combination of B2,P13 and WMAP Polarization data.
基金supported by the National Basic Research Program of China(2009CB824800)the National Natural Science Foundation of China(11033003)+1 种基金the National Natural Science Foundation for Young Scientistsof China (11203024)the Youth Innovation Promotion Association,CAS
文摘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 K2 from the seven-year WMAP (WMAP7) data. This result is evidently incompatible with ～1000 K2 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.
