Dipole modulation of cosmic microwave background temperature and polarization

The cosmic microwave background (CMB) temperature anisotropies exhibit a large-scale dipolar power asymmetry. To determine whether this is due to a real, physical modulation or is simply a large statistical fluctuation requires the measurement of new modes. Here we forecast how well CMB polarization data from Planck and future experiments will be able to confirm or constrain physical models for modulation. Fitting several such models to the Planck temperature data allows us to provide predictions for polarization asymmetry. While for some models and parameters Planck polarization will decrease error bars on the modulation amplitude by only a small percentage, we show, importantly, that cosmic-variance-limited (and in some cases even Planck) polarization data can decrease the errors by considerably better than the expectation of $\sqrt 2$ based on simple $\ell$-space arguments. We project that if the primordial fluctuations are truly modulated (with parameters as indicated by Planck temperature data) then Planck will be able to make a 2$\sigma$ detection of the modulation model with 20-75% probability, increasing to 45-99% when cosmic-variance-limited polarization is considered. We stress that these results are quite model dependent. Cosmic variance in temperature is important: combining statistically isotropic polarization with temperature data will spuriously increase the significance of the temperature signal with 30% probability for Planck.Comment: 15 pages, 11 figures, 2 table

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“…These expressions agree with those in [46]. Note that ±2 ξ 0 m m = 0 (for m = 0), so we expect , coupling in E and B modes.…”

Section: Discussionsupporting

confidence: 87%

Testing physical models for dipolar asymmetry with CMB polarization

et al. 2017

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“…The imaginary part of the form factor has been chosen so that we obtain the power required to fit the data [45,46]. We point out that the dipolar power spectrum was found to decay by approximately one power of k higher than the standard scale invariant power spectrum [45].…”

Section: Power Spectrum In Frw Backgroundmentioning

confidence: 99%

“…The hemispherical anisotropy is parametrized in terms of the phenomenological dipole modulation model [30][31][32][33]46]. It has been argued [18][19][20] that the power spectrum obtained in [17] is not acceptable since it produces imaginary correlations among temperature spherical harmonic coefficients, a lm 's, while they should be real.…”

Section: Introductionmentioning

confidence: 99%

Cosmological power spectrum in a noncommutative spacetime

2016

Self Cite

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We propose a generalized star product which deviates from the standard product when the fields at evaluated at different space-time points. This produces no changes in the standard Lagrangian density in noncommutative space-time but produces a change in the cosmological power spectrum. We show that the generalized star product leads to physically consistent results and can fit the observed data on hemispherical anisotropy in the cosmic microwave background radiation.

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“…SI violation may occur due to weak lensing (Rotti et al 2011), Doppler boost due to the motion of our galaxy with respect to the CMB rest frame Hanson & Lewis 2009;Yasini & Pierpaoli 2017a,b, 2016 etc. Recent experiments also show dipole modulation of the low multipoles of the CMB sky due to unexplained sources (Ghosh et al 2016;Fernandez-Cobos et al 2014;Mukherjee et al 2016). Apart from these cosmological effects, there can be many other observational artifacts.…”

Section: Introductionmentioning

confidence: 99%

sitoolbox: A package for Bayesian estimation of the isotropy violation in the CMB sky

Das

2019

Monthly Notices of the Royal Astronomical Society

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The standard model of cosmology predicts a statistically isotropic (SI) CMB sky. However, the SI violation signals are always present in an observed sky-map. Different cosmological artifacts, measurement effects and unavoidable effects during data analysis etc. may lead to isotropy violation in an otherwise SI sky. Therefore, a proper data analysis technique should calculate all these SI violation signals, so that they can be matched with SI violation signals from the known sources and then conclude if there is any intrinsic SI violation in the CMB sky. In one of our recent works, we presented a general Bayesian formalism for measuring the isotropy violation signals in the CMB sky in presence of an idealized isotropic noise. In this paper, we have extended the mechanism and develop a software package, SIToolBox, for measuring SI violation in presence of anisotropic noise and masking.

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Dipole modulation of cosmic microwave background temperature and polarization

Cited by 20 publications

References 61 publications

Testing physical models for dipolar asymmetry with CMB polarization

Testing physical models for dipolar asymmetry with CMB polarization

Cosmological power spectrum in a noncommutative spacetime

sitoolbox: A package for Bayesian estimation of the isotropy violation in the CMB sky

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