Breakdown of rotational invariance of the primordial power spectrum manifests in the statistical anisotropy of the observed Cosmic Microwave Background (CMB) radiation. Hemispherical power asymmetry in the CMB may be caused due to a dipolar modulation, indicating the presence of a preferred direction. Appropriately re-scaled local variance maps of the CMB temperature anisotropy data effectively encapsulate this dipolar pattern. As a first-of-its-kind method, we train Artificial Neural Networks (ANNs) with such local variances as input features to distinguish statistically isotropic CMB maps from dipole modulated ones. Our trained ANNs are able to predict components of the amplitude times the unit vector of the preferred direction for mixed sets of modulated and unmodulated maps, with goodness of fit ($R^2$) scores $>0.97$ for full sky, and $>0.96$ for partial sky coverage. On all observed foreground-cleaned CMB maps, the ANNs detect the dipolar modulation signal with overall consistent values of amplitudes and directions. This detection is significant at $97.21\%-99.38\%$ C.L. for all full sky maps, and at $98.34\%-100\%$ C.L. for all partial sky maps. Robustness of the signal holds across full and partial skies, various foreground cleaning methods, inpainting algorithms, instruments and all the different periods of observation for Planck and WMAP satellites. The significant and robust detection of the signal, in addition to the consistency of values of amplitude and directions, as found independent of any pre-existing methods, further mitigates the criticisms of look-elsewhere effects and a posteriori inferences for the preferred dipole direction in the CMB.
We perform a comparison of WMAP 9-year (WMAP9) and Planck 2015 cosmic microwave background (CMB) temperature power spectra across multipoles $30\leq\ell\leq1200$. 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 $1σ$. 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 $0.66σ$ level. We also show that changing the fiducial power spect…
Statistical isotropy (SI) of Cosmic Microwave Background (CMB) fluctuations is a key observational test to validate the cosmological principle underlying the standard model of cosmology. While a detection of SI violation would have immense cosmological ramification, it is important to recognise their possible origin in systematic effects of observations. WMAP seven year (WMAP-7) release claimed significant deviation from SI in the bipolar spherical harmonic (BipoSH) coefficients $A_{ll}^{20}$ and $A_{l-2l}^{20}$. Here we present the first explicit reproduction of the measurements reported in W…
In this article, we describe a new estimate of the Cosmic Microwave Background (CMB) intensity map reconstructed by a joint analysis of the full Planck 2015 data (PR2) and WMAP nine-years. It provides more than a mere update of the CMB map introduced in (Bobin et al. 2014b) since it benefits from an improvement of the component separation method L-GMCA (Local-Generalized Morphological Component Analysis) that allows the efficient separation of correlated components (Bobin et al. 2015). Based on the most recent CMB data, we further confirm previous results (Bobin et al. 2014b) showing that the …
The "dark flow" dipole is a statistically significant dipole found at the position of galaxy clusters in filtered maps of Cosmic Microwave Background (CMB) temperature anisotropies. The dipole measured in WMAP 3, 5 and 7 yr data releases was 1) mutually consistent, 2) roughly aligned with the all-sky CMB dipole and 3) correlated with clusters' X-ray luminosity. We analyzed WMAP 9 yr and the 1st yr Planck data releases using a catalog of 980 clusters outside the Kp0 mask to test our earlier findings. The dipoles measured on these new data sets are fully compatible with our earlier estimates, be…
In recent years, there have been a large number of studies which support violation of statistical isotropy. Meanwhile, there are some studies which also found inconsistency. We use the power tensor method defined earlier in the literature to study the new CMBR data. The orientation of these three orthogonal vectors, as well as the power associated with each vector, contains information about possible violation of statistical isotropy. This information is encoded in two entropy measures, the power-entropy and alignment- entropy. We apply this method to WMAP 9-year and PLANCK data. Here, we also…
We present a CMB large-scale polarization dataset obtained by combining WMAP Ka, Q and V with Planck 70 GHz maps. We employ the legacy frequency maps released by the WMAP and Planck collaborations and perform our own Galactic foreground mitigation technique, which relies on Planck 353 GHz for polarized dust and on Planck 30 GHz and WMAP K for polarized synchrotron. We derive a single, optimally-noise-weighted, low-residual-foreground map and the accompanying noise covariance matrix. These are shown, through $χ^2$ analysis, to be robust over an ample collection of Galactic masks. We use this da…
We revisit the alignments of the largest structures observed in the cosmic microwave background (CMB) using the seven and nine-year WMAP and first-year Planck data releases. The observed alignments -- the quadrupole with the octopole and their joint alignment with the direction of our motion with respect to the CMB (the dipole direction) and the geometry of the Solar System (defined by the Ecliptic plane) -- are generally in good agreement with results from the previous WMAP data releases. However, a closer look at full-sky data on the largest scales reveals discrepancies between the earlier W…
The lack of large-angle correlations in the observed microwave background temperature fluctuations persists in the final-year maps from WMAP and the first cosmological data release from Planck. We find a statistically robust and significant result: p-values for the missing correlations lying below 0.24 per cent (i.e. evidence at more than 3 sigma) for foreground cleaned maps, in complete agreement with previous analyses based upon earlier WMAP data. A conservative cut-sky analysis of the Planck HFI 100 GHz frequency band, the `cleanest CMB channel', returns a p-value as small as 0.03 per cent,…
Both WMAP and PLANCK missions reported the extremely Cold Spot (CS) centered at Galactic coordinate ($l=209^{\circ}$, $b=-57^{\circ}$) in CMB map. In this paper, we study the local non-Gaussianity of CS by defining the local Minkowski functions. We find that the third Minkowski function $ν_2$ is quite sensitive to the non-Gaussianity caused by CS. Compared with the random Gaussian simulations, WMAP CS deviates from Gaussianity at more than 99% confident level at the scale $R\sim10^{\circ}$. Meanwhile, we find that cosmic texture provides an excellent explanation for these anomalies related to …
The reionization optical depth is the most poorly determined of the six $Λ$CDM parameters fit to CMB anisotropy data. Instrumental noise and systematics have prevented uncertainties from reaching their cosmic variance limit. At present, the datasets providing the most statistical constraining power are the WMAP, Planck LFI, and Planck HFI full-sky polarization maps. As the reprocessed HFI data with reduced systematics are not yet publicly unavailable, we examine determinations of $τ$ using 9-year WMAP and 2015 Planck LFI data, with an emphasis on characterizing potential systematic bias result…
The purpose of this work is to characterize the diffuse Galactic polarized synchrotron. We present EE, BB, and EB power spectra estimated cross-correlating Planck and WMAP polarization frequency maps at 23 and 30 GHz, for a set of six sky regions covering from 30% to 94% of the sky. The EE and BB angular power spectra show a steep decay of the spectral amplitude as a function of multipole, approximated by a power law with power indices around -2.9 for both components. The B/E ratio is about 0.22. The EB cross-component is compatible with zero at 1$σ$, with upper constraint on the EB/EE ratio o…
The remarkable progress in cosmic microwave background (CMB) studies over past decade has led to the era of precision cosmology in striking agreement with the $Λ$CDM model. However, the lack of power in the CMB temperature anisotropies at large angular scales (low-$\ell$), as has been confirmed by the recent Planck data also (up to $\ell=40$), although statistically not very strong (less than $3σ$), is still an open problem. One can avoid to seek an explanation for this problem by attributing the lack of power to cosmic variance orcan look for explanations i.e., different inflationary potentia…
