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Register a new userComparing Planck and WMAP: Maps, Spectra, and Parameters
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D. Larson
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We examine the consistency of WMAP9 and Planck data. We compare sky maps, power spectra, and inferred LCDM cosmological parameters. Residual dipoles are seen in the WMAP and Planck sky map differences, but are consistent within the uncertainties and are not large enough to explain the widely-noted differences in angular power spectra at higher l. After removing residual dipoles and galactic foregrounds, the residual difference maps exhibit a quadrupole and other large-scale systematic structure. We identify this structure as possibly originating from Plancks beam sidelobe pick-up, but note that it appears to have insignificant cosmological impact. We develop an extension of the internal linear combination technique and find features that plausibly originate in the Planck data. We examine LCDM model fits to the angular power spectra and conclude that the ~2.5% difference in the spectra at multipoles greater than l~100 are significant at the 3-5 sigma level. We revisit the analysis of WMAPs beam data and conclude that previously-derived uncertainties are robust and cannot explain the power spectrum differences. Finally, we examine the consistency of the LCDM parameters inferred from each data set taking into account the fact that both experiments observe the same sky, but cover different multipole ranges, apply different sky masks, and have different noise. While individual parameter values agree within the uncertainties, the 6 parameters taken together are discrepant at the ~6 sigma level, with chi2=56 for 6 dof (PTE = 3e-10). Of the 6 parameters, chi2 is best improved by marginalizing over Omega_c h^2, giving chi2=5.2 for 5 degrees of freedom. We find that perturbing the WMAP window function by its dominant beam error profile has little effect on Omega_c h^2, while perturbing the Planck window function by its corresponding error profile has a much greater effect on Omega_c h^2.
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(Abridged) We present the angular power spectra derived from the 7-year maps and discuss the cosmological conclusions that can be inferred from WMAP data alone. The third acoustic peak in the TT spectrum is now well measured by WMAP. In the context of a flat LambdaCDM model, this improvement allows us to place tighter constraints on the matter density from WMAP data alone, and on the epoch of matter-radiation equality, The temperature-polarization (TE) spectrum is detected in the 7-year data with a significance of 20 sigma, compared to 13 sigma with the 5-year data. The low-l EE spectrum, a measure of the optical depth due to reionization, is detected at 5.5 sigma significance when averaged over l = 2-7. The BB spectrum, an important probe of gravitational waves from inflation, remains consistent with zero. The upper limit on tensor modes from polarization data alone is a factor of 2 lower with the 7-year data than it was using the 5-year data (Komatsu et al. 2010). We test the parameter recovery process for bias and find that the scalar spectral index, ns, is biased high, but only by 0.09 sigma, while the remaining parameters are biased by < 0.15 sigma. The improvement in the third peak measurement leads to tighter lower limits from WMAP on the number of relativistic degrees of freedom (e.g., neutrinos) in the early universe: Neff > 2.7 (95% CL). Also, using WMAP data alone, the primordial helium mass fraction is found to be YHe = 0.28+0.14-0.15, and with data from higher-resolution CMB experiments included, we now establish the existence of pre-stellar helium at > 3 sigma (Komatsu et al. 2010).
We perform a comparison of WMAP 9-year (WMAP9) and Planck 2015 cosmic microwave background (CMB) temperature power spectra across multipoles $30leqellleq1200$. We generate simulations to estimate the correlation between the two datasets due to cosmic variance from observing the same sky. We find that their spectra are consistent within $1sigma$. While we do not implement the optimal $C^{-1}$ estimator on WMAP maps as in the WMAP9 analysis, we demonstrate that the change of pixel weighting only shifts our results at most at the $0.66sigma$ level. We also show that changing the fiducial power spectrum for simulations only impacts the comparison at around $0.1sigma$ level. We exclude $ell<30$ both because WMAP9 data were included in the Planck 2015 $ell<30$ analysis, and because the cosmic variance uncertainty on these scales is large enough that any remaining systematic difference between the experiments is extremely unlikely to affect cosmological constraints. The consistency shown in our analysis provides high confidence in both the WMAP9 temperature power spectrum and the overlapping multipole region of Planck 2015s, virtually independent of any assumed cosmological model. Our results indicate that cosmological model differences between Planck and WMAP do not arise from measurement differences, but from the high multipoles not measured by WMAP.
This paper describes the processing applied to the Planck High Frequency Instrument (HFI) cleaned, time-ordered information to produce photometrically calibrated maps in temperature and (for the first time) in polarization. The data from the entire 2.5 year HFI mission include almost five independent full-sky surveys. HFI observes the sky over a broad range of frequencies, from 100 to 857 GHz. To obtain the best accuracy on the calibration over such a large range, two different photometric calibration schemes have been used. The 545 and 857 GHz data are calibrated using models of planetary atmospheric emission. The lower frequencies (from 100 to 353 GHz) are calibrated using the time-variable cosmological microwave background dipole, which we call the orbital dipole. This source of calibration only depends on the satellite velocity with respect to the solar system. Using a CMB temperature of 2.7255 +/- 0.0006 K, it permits an independent measurement of the amplitude of the CMB solar dipole (3364.3 +/- 1.5 mu K) which is approximatively 1sigma higher than the WMAP measurement with a direction that is consistent between both experiments. We describe the pipeline used to produce the maps of intensity and linear polarization from the HFI timelines, and the scheme used to set the zero level of the maps a posteriori. We also summarize the noise characteristics of the HFI maps in the 2015 Planck data release and present some null tests to assess their quality. Finally, we discuss the major systematic effects and in particular the leakage induced by flux mismatch between the detectors that leads to spurious polarization signal.
We present a novel estimate of the cosmological microwave background (CMB) map by combining the two latest full-sky microwave surveys: WMAP nine-year and Planck PR1. The joint processing benefits from a recently introduced component separation method coined local-generalized morphological component analysis (LGMCA) based on the sparse distribution of the foregrounds in the wavelet domain. The proposed estimation procedure takes advantage of the IRIS 100 micron as an extra observation on the galactic center for enhanced dust removal. We show that this new CMB map presents several interesting aspects: i) it is a full sky map without using any inpainting or interpolating method, ii) foreground contamination is very low, iii) the Galactic center is very clean, with especially low dust contamination as measured by the cross-correlation between the estimated CMB map and the IRIS 100 micron map, and iv) it is free of thermal SZ contamination.
This paper presents the Planck 2015 likelihoods, statistical descriptions of the 2-point correlations of CMB data, using the hybrid approach employed previously: pixel-based at $ell<30$ and a Gaussian approximation to the distribution of spectra at higher $ell$. The main improvements are the use of more and better processed data and of Planck polarization data, and more detailed foreground and instrumental models, allowing further checks and enhanced immunity to systematics. Progress in foreground modelling enables a larger sky fraction. Improvements in processing and instrumental models further reduce uncertainties. For temperature, we perform an analysis of end-to-end instrumental simulations fed into the data processing pipeline; this does not reveal biases from residual instrumental systematics. The $Lambda$CDM cosmological model continues to offer a very good fit to Planck data. The slope of primordial scalar fluctuations, $n_s$, is confirmed smaller than unity at more than 5{sigma} from Planck alone. We further validate robustness against specific extensions to the baseline cosmology. E.g., the effective number of neutrino species remains compatible with the canonical value of 3.046. This first detailed analysis of Planck polarization concentrates on E modes. At low $ell$ we use temperature at all frequencies and a subset of polarization. The frequency range improves CMB-foreground separation. Within the baseline model this requires a reionization optical depth $tau=0.078pm0.019$, significantly lower than without high-frequency data for explicit dust monitoring. At high $ell$ we detect residual errors in E, typically O($mu$K$^2$); we recommend temperature alone as the high-$ell$ baseline. Nevertheless, Planck high-$ell$ polarization allows a separate determination of $Lambda$CDM parameters consistent with those from temperature alone.
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