Searching for primordial non-Gaussianity in Planck CMB maps using a combined estimator

Novaes, Camila P.; Bernui, Armando; Ferreira, Ivan Soares; Wuensche, Carlos Alexandre

doi:10.1088/1475-7516/2014/01/018

Cited by 14 publications

(22 citation statements)

References 188 publications

(382 reference statements)

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“…In Ref. [20], it was observed a larger amplitude of the perimeter calculated from Planck map compared with those calculated from the synthetic ones. This problem is minimized performing a smoothing procedure on both maps (see Ref.…”

Section: Estimator Application To Synthetic and Planck Datamentioning

confidence: 93%

“…After this whole procedure the estimator is ready to be applied in different CMB maps, synthetic (to validate its performance) and real maps, allowing its classification about their level of NG. It is important to emphasize that the estimator we are dealing with here is the same addressed in our previous work [20], but this time we can interpret the NN's output in a way to directly estimate the f NL parameter.…”

Section: The Combined Estimatormentioning

confidence: 99%

“…In the next subsections we summarize the main concepts of each tool and how they are combined to obtain the estimator (see [20] for details), in addition to explaining the new approach to addressing the NN's output.…”

Section: The Combined Estimatormentioning

confidence: 99%

“…[20], to test the efficiency of our estimator in the current analyses. This is done counting the number of success (called hits) of the NN in the classification of the vector y corresponding to a map of the test set.…”

Section: Tests On Synthetic Data: Ef Fects Of the Galactic Residualsmentioning

confidence: 99%

“…In [20] we have presented a statistical estimator which proved to be quite sensitive to detect tiny primordial NG of local type, endowed in synthetic Gaussian CMB maps, besides its capability to differentiates between primary and secondary (inhomogeneous noise) NGs. This method used the Minkowski Functionals (MFs) [21] calculated from a set of Monte Carlo (MC) CMB maps as input data for the training of an Artificial Neural Network (NN) [22], that classifies each synthetic map of a second dataset according to the presence and level of NG.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A neural-network based estimator to search for primordial non-Gaussianity in Planck CMB maps

Novaes

Bernui

Ferreira

et al. 2015

J. Cosmol. Astropart. Phys.

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Abstract. We present an upgraded combined estimator, based on Minkowski Functionals and Neural Networks, with excellent performance in detecting primordial non-Gaussianity in simulated maps that also contain a weighted mixture of Galactic contaminations, besides real pixel's noise from Planck cosmic microwave background radiation data. We rigorously test the efficiency of our estimator considering several plausible scenarios for residual non-Gaussianities in the foreground-cleaned Planck maps, with the intuition to optimize the training procedure of the Neural Network to discriminate between contaminations with primordial and secondary non-Gaussian signatures. We look for constraints of primordial local non-Gaussianity at large angular scales in the foreground-cleaned Planck maps. For the SMICA map we found f NL = 33 ± 23, at 1σ confidence level, in excellent agreement with the WMAP-9yr and Planck results. In addition, for the other three Planck maps we obtain similar constraints with values in the interval f NL ∈ [33, 41], concomitant with the fact that these maps manifest distinct features in reported analyses, like having different pixel's noise intensities.

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Section: Estimator Application To Synthetic and Planck Datamentioning

confidence: 93%

Section: The Combined Estimatormentioning

confidence: 99%

Section: The Combined Estimatormentioning

confidence: 99%

Section: Tests On Synthetic Data: Ef Fects Of the Galactic Residualsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A neural-network based estimator to search for primordial non-Gaussianity in Planck CMB maps

Novaes

Bernui

Ferreira

et al. 2015

J. Cosmol. Astropart. Phys.

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Mapping possible non-Gaussianity in thePlanckmaps

Bernui

Rebouças

2015

A&A

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Context. The study of the non-Gaussianity of the temperature fluctuations of cosmic background radiation (CMB) can be used to break the degeneracy between the inflationary models and to test alternative scenarios of the early universe. However, there are several sources of non-Gaussian contaminants in the CMB data, which make a convincing extraction of primordial non-Gaussianity into an ambitious observational and statistical enterprise. It is conceivable that no single statistical estimator can be sensitive to all forms and levels of non-Gaussianity that may be present in observed CMB data. In recent works a statistical procedure based upon the calculation of the skewness and kurtosis of the patches of CMB sky sphere has been proposed and used to find out significant large-angle deviation from Gaussianity in the foreground-reduced WMAP maps. Aims. Here we address the question of how previous recent analyses of Gaussianity of WMAP maps are modified if the nearly full-sky foreground-cleaned Planck maps are used, therefore extending and complementing such an examination in several regards. Methods. Once the foregrounds are cleaned through different component separation procedures, each of the resulting Planck maps is then tested for Gaussianity. We determine quantitatively the effects for Gaussianity when masking the foreground-cleaned Planck maps with the , , and U73 Planck masks.Results. We show that although the foreground-cleaned Planck maps present significant deviation from Gaussianity of different degrees when the less severe  and  are used, they become consistent with Gaussianity as detected by our indicator S when masked with the union U73 mask. A slightly smaller consistency with Gaussianity is found when the K indicator is employed, which seems to be associated with the large-angle anomalies reported by the Planck team. Finally, we examine the robustness of the Gaussianity analyses with respect to the real pixel's noise as given by the Planck team, and show that no appreciable changes arise when it is incorporated into the maps. The results of our analyses provide important information concerning Gaussianity of the foreground-cleaned Planck maps when diverse cut-sky masks are used.

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North-South non-Gaussian asymmetry in Planck CMB maps

Bernui¹,

Oliveira²,

Pereira³

2014

J. Cosmol. Astropart. Phys.

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We report the results of a statistical analysis performed with the four foregroundcleaned Planck maps by means of a suitably defined local-variance estimator. Our analysis shows a clear dipolar structure in Planck's variance map pointing in the direction (l, b) (220 • , −32 • ), thus consistent with the North-South asymmetry phenomenon. Surprisingly, and contrary to previous findings, removing the CMB quadrupole and octopole makes the asymmetry stronger. Our results show a maximal statistical significance, of 98.1% CL, in the scales ranging from = 4 to = 500. Additionally, through exhaustive analyses of the four foreground-cleaned and individual frequency Planck maps, we find unlikely that residual foregrounds could be causing this dipole variance asymmetry. Moreover, we find that the dipole gets lower amplitudes for larger masks, evidencing that most of the contribution to the variance dipole comes from a region near the galactic plane. Finally, our results are robust against different foreground cleaning procedures, different Planck masks, pixelization parameters, and the addition of inhomogeneous real noise. IntroductionThe temperature fluctuations of the Cosmic Microwave Background radiation (CMB), recently released by the Planck collaboration [1], confirmed with outstanding precision the concordance cosmological model, ΛCDM [2][3][4]. Such exquisite set of cosmological information allows us to test two fundamental properties of the universe expected after the standard inflationary phase [5][6][7][8], namely that the CMB field is, at large-angles, nearly Gaussian and statistically isotropic (see, e.g., [9, 10] and refs. therein).Previous studies using WMAP data indicate significant departure from either gaussianity or statistical isotropy at the largest angular scales -an unexpected result in the ΛCDM model , though possibly disputable [58]. These phenomena, also called anomalies, have been now confirmed with similar high confidence levels, ∼ 3σ, by the Planck collaboration with CMB foreground-cleaned maps [10]. On the other side, only small magnitude Gaussian deviations from primordial origin have been detected in Planck data [59,60]. However, there are more potential sources of non-Gaussianity (NG) in the CMB data than just primordial NG [61][62][63][64][65][66]. These include galactic foregrounds remnants and secondary anisotropies coming from processes after the last scattering surface [60,[67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82]. In particular, Gaussian analyses for large angular scales are delicate because galactic foregrounds contaminations are not completely understood and, as a consequence, galactic cut-sky masks are still necessary in CMB data analyses [60]. Monteserín et al. (2008) [83] reported an anomalously low variance distribution in WMAP3 maps at 98.7% CL. Cruz et al. (2011)[84] confirmed this result in WMAP5 and WMAP7 data, also pointing that some regions near the galactic plane present an anomalously high variance (95.6% CL) in the south ecliptic hemisphere. Their ...

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Searching for primordial non-Gaussianity in Planck CMB maps using a combined estimator

Cited by 14 publications

References 188 publications

A neural-network based estimator to search for primordial non-Gaussianity in Planck CMB maps

A neural-network based estimator to search for primordial non-Gaussianity in Planck CMB maps

Mapping possible non-Gaussianity in thePlanckmaps

North-South non-Gaussian asymmetry in Planck CMB maps

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