Alignment tests for low CMB multipoles

Abramo, L. Raul; Bernui, Armando; Ferreira, Ivan Soares; Villela, T.; Wuensche, Carlos Alexandre

doi:10.1103/physrevd.74.063506

Cited by 65 publications

(78 citation statements)

References 52 publications

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“…Other anomalies were found in the WMAP data that were not expected according to the ΛCDM model either, such as the alignment between the quadrupole and octopole (e.g. Bielewicz et al 2004;Schwarz et al 2004;Copi et al 2004;de Oliveira-Costa et al 2004;Bielewicz et al 2005;Land & Magueijo 2005;Copi et al 2006;Abramo et al 2006;Frommert & Ensslin 2010;Gruppuso & Burigana 2010), the low quadrupole and octopole amplitudes (e.g., Mukherjee & Wang 2003;Ayata et al 2010;Cayon 2010;Cruz et al 2011), the north-south asymmetry (e.g., Eriksen et al 2004a;Hansen et al 2004a;Eriksen et al 2004b;Hansen et al 2004b;Donoghue et al 2005;Hoftuft et al 2009;Paci et al 2010;Pietrobon et al 2010;Vielva & Sanz 2010), the anomalous alignment of the CMB features toward the Ecliptic poles (e.g., Wiaux et al 2006;Vielva et al 2007), and the cold spot (e.g., Vielva et al 2004;Cruz et al 2005Cruz et al , 2007Vielva 2010).…”

Section: Introductionmentioning

confidence: 99%

Asymmetries in the angular distribution of the cosmic microwave background

Santos

Villela

Wuensche

2012

A&A

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Context. Intriguing features in the angular distribution of the cosmic microwave background (CMB), such as the north-south asymmetry, were reported in the one-and three-year Wilkinson Microwave Anisotropy Probe (WMAP) data and should be studied in detail. We investigate some of these asymmetries in the CMB temperature angular distribution considering the ΛCDM model in the three, five, and seven year WMAP data.Aims. We aim to analyze the four quadrants of the internal linear combination (ILC) CMB maps using three different Galactic cuts: the WMAP KQ85 mask, a |b| < 10 • Galactic cut, and the WMAP KQ85 mask + |b| < 10 • Galactic cut. Methods. We used the two-point angular correlation function (TPCF) in the WMAP maps for each of their quadrants. The same procedure was performed for 1000 Monte Carlo (MC) simulations that were produced using the WMAP team ΛCDM best-fit power spectrum. In addition, we changed the quadrupole and octopole amplitudes obtained from the ΛCDM model spectrum. We changed this to fit the quadrupole and octopole amplitudes to their observable values from the WMAP data. We repeated the analysis for the 1000 simulations of this modified ΛCDM model, hereafter MΛCDM. Results. Our analysis showed asymmetries between the southeastern quadrant (SEQ) and the other quadrants (southwestern quadrant (SWQ), northeastern quadrant (NEQ) and northwestern quadrant (NWQ)). Over all WMAP ILC maps, the probability for the occurrence of the SEQ-NEQ, SEQ-SWQ and SEQ-NWQ asymmetries varies from 0.1% (SEQ-NEQ) to 8.5% (SEQ-SWQ) using the KQ85 mask and the KQ85 mask + |b| < 10 • Galactic cut, respectively. We also calculated the probabilities for the MΛCDM using only the KQ85 mask and found no significant differences in the results. Moreover, the cold spot region located in the SEQ quadrant was covered with masks of 5, 10 and 15 degrees radius and again the results remained unchanged. Furthermore, this analysis was repeated for random regions in the SEQ quadrant with a 15-degree mask and the SEQ quadrant still remained asymmetric with respect to the other quadrants of the CMB map. Conclusions. We found an excess of power in the TPCF at scales >100 degrees in the SEQ with respect to the other quadrants that is independent of the Galactic cut used. Moreover, we tested a possible relation between the cold spot and the SEQ excess of power and found no evidence for it. Finally, we could not find any specific region within the SEQ that might be considered responsible for the quadrant asymmetry.

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Section: Introductionmentioning

confidence: 99%

Asymmetries in the angular distribution of the cosmic microwave background

Santos

Villela

Wuensche

2012

A&A

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“…(2)-(3) for higher multipoles -see, e.g., [20,24]. If a given foreground cures the quadrupole level and the quadrupole-octopole alignment at the cost of introducing anomalous alignments between other multipoles, then the overall likelihood of the resulting map should fall.…”

Section: A Higher Multipolesmentioning

confidence: 99%

“…For a complete treatment of statistical tests of isotropy, their P.D.F. 's, and an assessment of other sources of error see [24].…”

Section: Low Quadrupole and Alignmentsmentioning

confidence: 99%

Anomalies in the low CMB multipoles and extended foregrounds

2006

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We discuss how an extended foreground of the cosmic microwave background (CMB) can account for the anomalies in the low multipoles of the CMB anisotropies. The distortion needed to account for the anomalies is consistent with a cold spot with the spatial geometry of the Local Supercluster (LSC) and a temperature quadrupole of order ∆T 2 2 ≈ 50 µK 2 . If this hypothetic foreground is subtracted from the CMB data, the amplitude of the quadrupole (ℓ = 2) is substantially increased, and the statistically improbable alignment of the quadrupole with the octopole (ℓ = 3) is substantially weakened, increasing dramatically the likelihood of the "cleaned" maps. By placing the foreground on random locations and then computing the likelihood of the cleaned maps we can estimate the most likely place for this foreground. Although the 1-year WMAP data clearly points the location of this hypothetical foreground to the LSC or its specular image (i.e., the vicinity of the poles of the cosmic dipole axis), the three-year data seems to point to these locations as well as the north ecliptic pole. We show that this is consistent with the symmetries of the cosmic quadrupole. We also discuss a possible mechanism that could have generated this foreground: the thermal Sunyaev-Zeldovich effect caused by hot electrons in the LSC. We argue that the temperature and density of the hot gas which are necessary to generate such an effect, though in the upper end of the expected range of values, are marginally consistent with present observations of the X-ray background of spectral distortions of the CMB.PACS numbers: 98.65.Dx, 98.70.Vc, 98.80.Es

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“…1 However, since the polarization is not statistically independent of the temperature, chance fluctuations in the temperature map also manifest themselves in the polarization [6]. Here, we thus use the part of the polarization map which is uncorrelated with the temperature map as a statistically independent probe of the axis of evil.…”

Section: Introductionmentioning

confidence: 99%

“…However, in recent years, there have been claims of anomalies detected in the CMB temperature map with considerable significance, which seem to break statistical isotropy of the temperature fluctuations and thus to question the cosmological principle. Among these anomalies, there is a strong alignment between the preferred axes of the quadrupole and the octopole, which is commonly referred to as the axis of evil [3,1,11,16,15]. The claims of the existence of a preferred direction in the CMB temperature map have led to a discussion about whether this is simply due to a chance fluctuation in the CMB temperature map, if it can be blamed on local structures or on systematics in the measurement, or whether it is actually due to a preferred direction intrinsic to the geometry of the primordial Universe [4,12,17,8,13,18,10].…”

Section: Introductionmentioning

confidence: 99%

The Axis of Evil - A Polarization Perspective

Frommert¹,

Enßlin²

2010

Proceedings of International Workshop on Cosmic Structure and Evolution — PoS(Cosmology2009)

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We search for an unusual alignment of the preferred axes of the quadrupole and octopole, the so-called axis of evil, in the WMAP polarization data. We split the polarization map into a part correlated with the temperature and an uncorrelated part. We then determine the preferred axes for the quadrupole and octopole in the uncorrelated polarization map, which serves as a statistically independent probe of the axis of evil. We find that the axis of the quadrupole aligns with the axis of evil within our measurement precision, whereas the axis of the octopole does not. However, with our measurement uncertainty, the probability of at least one axis aligning by chance in an isotropic universe is of the order of 50 per cent. Nevertheless, our analysis of the axis of evil promises to be a powerful tool when applied to data expected from the Planck satellite. Structure and Evolution -Cosmology2009, International Workshop on Cosmic

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Alignment tests for low CMB multipoles

Cited by 65 publications

References 52 publications

Asymmetries in the angular distribution of the cosmic microwave background

Asymmetries in the angular distribution of the cosmic microwave background

Anomalies in the low CMB multipoles and extended foregrounds

The Axis of Evil - A Polarization Perspective

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