COSMIC MICROWAVE BACKGROUND POLARIZATION AND TEMPERATURE POWER SPECTRA ESTIMATION USING LINEAR COMBINATION OF<i>WMAP</i>5 YEAR MAPS

Samal, Pramoda Kumar; Saha, Rajib; Delabrouille, J.; Prunet, S.; Jain, Pankaj; Souradeep, T.

doi:10.1088/0004-637x/714/1/840

Cited by 16 publications

(20 citation statements)

References 65 publications

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“…Here we confine ourselves to the simple case of one foreground component following rigid frequency scaling and two frequency bands. This computation is useful to determine if the low‐ l bias (Saha et al 2008; Samal et al 2010) also leads to violation of statistical isotropy. We then numerically determine the effect of this bias and residual foregrounds on the alignment of quadrupole and octopole.…”

Section: Analysis Methodologymentioning

confidence: 99%

“…In the internal power spectrum estimation (IPSE) procedure (Saha, Jain & Souradeep 2006; Saha et al 2008; Samal et al 2010), the cleaning is performed by a blind procedure without making any explicit model for foregrounds. The foregrounds are removed by adding maps in harmonic space at different frequencies with suitable weights, chosen so as to minimize the foreground power.…”

Section: Introductionmentioning

confidence: 99%

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Effect of foregrounds on the cosmic microwave background radiation multipole alignment

Aluri

Samal

Jain

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We analyse the effect of foregrounds on the observed alignment of the cosmic microwave background radiation (CMBR) quadrupole and octopole. The alignment between these multipoles is studied by using a symmetry‐based approach which assigns a principal eigenvector (PEV) or an axis with each multipole. We determine the alignment between these multipoles and its significance using the internal linear combination (ILC) 5‐ and 7‐yr maps. We also use the maps obtained by applying the internal power spectrum estimation (IPSE) procedure on the corresponding Wilkinson Microwave Anisotropy Probe data sets to assess its significance. The effect of foreground cleaning is studied in detail within the framework of the IPSE method both analytically and numerically. By using simulated CMBR data, including foregrounds and detector noise, we study how the PEVs of the simulated pure CMB maps differ from those of the corresponding clean maps. We find that, in general, the shift in the PEVs is relatively small and in random directions. Because of the random nature of the shift we conclude that the residual foregrounds can only lead to misalignment rather than cause alignment of multipoles. We also directly estimate the significance of the observed alignment by using simulated clean maps. We find that the results in this case are identical to those obtained by simple analytic estimates or by using simulated pure CMB maps.

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Section: Analysis Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of foregrounds on the cosmic microwave background radiation multipole alignment

Aluri

Samal

Jain

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…In earlier publications Souradeep et al 2006;Saha et al 2008;Samal et al 2010) the authors reported that the multipole-based Internal Linear Combination (ILC) method gives rise to a negative bias in its power spectrum at the low multipoles. The bias appears due to a mere chance correlation between CMB and foregrounds at large angles due to availability of only a small number of modes in the large scales on the sky.…”

Section: Power Spectrummentioning

confidence: 99%

“…One of the most important aspects of the method is that it continues to preserve a CMB signal even if it possesses a non-Gaussian nature which may result due to any possible primordial and/or secondary effects, e.g., CMB weak lensing. A detailed account on several other foreground removal methods may be found in existing literature (Brandt et al 1994;Tegmark & Efstathiou 1996;Bouchet & Gispert 1999;Bennett et al 2003;Tegmark et al 2003 Leach et al 2008;Delabrouille et al 2009;Samal et al 2010;Pietrobon et al 2010). For discussions about searching for non-Gaussianity in foreground-minimized CMB maps we refer to Räth et al (2009), Barreiro et al (2000), Banday et al (2000), Raeth et al (2011), Hou et al (2010, and Bernui & Rebouças (2010).…”

Section: Introductionmentioning

confidence: 99%

A Foreground-Cleaned Cosmic Microwave Background Map From Non-Gaussianity Measurement

Saha

2011

ApJ

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In this Letter, we present a new method to estimate a foreground-cleaned cosmic microwave background (CMB) map at a resolution of 1• by minimizing the non-Gaussian properties of the cleaned map which arise dominantly due to diffuse foreground emission components from the Milky Way. We employ simple kurtosis statistic as the measure of non-Gaussian properties and perform a linear combination of five frequency maps provided by the Wilkinson Microwave Anisotropy Probe (WMAP) in its seven-year data release in such a way that the cleaned map has a minimum kurtosis which leads to a non-Gaussianity-minimized, foreground-cleaned CMB map. We validate the method by performing Monte Carlo simulations. To minimize any residual foreground contamination from the cleaned map we flag out the region near the galactic plane based upon results from simulations. Outside the masked region our new estimate of the CMB map matches well with the WMAP's Internal Linear Combination (ILC) map. A simple pseudo-C l -based CMB TT power spectrum derived from the non-Gaussianity minimized map reproduces the earlier results of WMAP's power spectrum. An important advantage of the method is that it does not introduce any negative bias in angular power spectrum in the low multipole regime, unlike usual ILC method. Comparing our results with the previously published results we argue that CMB results are robust with respect to specific foreground removal algorithms employed.

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“…Until now, the analysis of WMAP/CMB data has been mainly made using the whole sky area except for strongly contaminated regions Nolta et al 2009;Larson et al 2011;Saha et al 2006Saha et al , 2008Souradeep et al 2006;Eriksen et al 2007a;Samal et al 2010;Basak & Delabrouille 2012). On the other hand, there has been less studies on the power spectrum measurement on partial regions of the sky (e.g., Eriksen et al 2004b;Hansen et al 2004a,b;Ansari et al 2010;Yoho et al 2011;Chiang & Chen 2012).…”

Section: Introductionmentioning

confidence: 99%

Local Anomalies Around the Third Peak in the CMB Angular Power Spectrum of Wmap 7-Year Data

Ko¹,

Park²,

Hwang³

2013

Journal of The Korean Astronomical Society

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We estimate the power spectra of the cosmic microwave background radiation (CMB) temperature anisotropy in localized regions of the sky using the Wilkinson Microwave Anisotropy Probe (WMAP) 7-year data. We find that the north and south hat regions at high Galactic latitude (|b| ≥ 30• ) show an anomaly in the power spectrum amplitude around the third peak, which is statistically significant up to 3σ. We try to explain the cause of the observed anomaly by analyzing the low Galactic latitude (|b| < 30• ) regions where the galaxy contamination is expected to be stronger, and the regions weakly or strongly dominated by WMAP instrument noise. We also consider the possible effect of unresolved radio point sources. We find another but less statistically significant anomaly in the low Galactic latitude north and south regions whose behavior is opposite to the one at high latitude. Our analysis shows that the observed north-south anomaly at high latitude becomes weaker on regions with high number of observations (weak instrument noise), suggesting that the anomaly is significant at sky regions that are dominated by the WMAP instrument noise. We have checked that the observed north-south anomaly has weak dependences on the bin-width used in the power spectrum estimation, and on the Galactic latitude cut. We also discuss the possibility that the detected anomaly may hinge on the particular choice of the multipole bin around the third peak. We anticipate that the issue of whether or not the anomaly is intrinsic one or due to WMAP instrument noise will be resolved by the forthcoming Planck data.

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COSMIC MICROWAVE BACKGROUND POLARIZATION AND TEMPERATURE POWER SPECTRA ESTIMATION USING LINEAR COMBINATION OFWMAP5 YEAR MAPS

Cited by 16 publications

References 65 publications

Effect of foregrounds on the cosmic microwave background radiation multipole alignment

Effect of foregrounds on the cosmic microwave background radiation multipole alignment

A Foreground-Cleaned Cosmic Microwave Background Map From Non-Gaussianity Measurement

Local Anomalies Around the Third Peak in the CMB Angular Power Spectrum of Wmap 7-Year Data

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