Direction dependence of cosmological parameters due to cosmic hemispherical asymmetry

Abstract

Persistent evidence for a cosmic hemispherical asymmetry in the temperature field of cosmic microwave background (CMB) as observed by both WMAP as well as PLANCK increases the possibility of its cosmological origin. Presence of this signal may lead to different values for the standard model cosmological parameters in different directions, and that can have significant implications for other studies where they are used. We investigate the effect of this cosmic hemispherical asymmetry on cosmological parameters using non-isotropic Gaussian random simulations injected with both scale dependent and scale independent modulation strengths. Our analysis shows that $A_s$ and $n_s$ are the most susceptible parameters to acquire position dependence across the sky for the kind of isotropy breaking phenomena under study. As expected, we find maximum variation arises for the case of scale independent modulation of CMB anisotropies. We find that scale dependent modulation profile as seen in PLANCK data could lead to only $1.25\sigma$ deviation in $A_s$ in comparison to its estimate from isotropic CMB sky.

14 pages, 5 figures. Matches the published version

References in corpus (28)

• Three Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Polarization Analysis
• Planck 2018 results. VII. Isotropy and Statistics of the CMB
• Hemispherical power asymmetry in the three-year Wilkinson Microwave Anisotropy Probe sky maps
• A Hemispherical Power Asymmetry from Inflation
• Power asymmetry in WMAP and Planck temperature sky maps as measured by a local variance estimator
• Superhorizon Perturbations and the Cosmic Microwave Background
• Probing the isotropy of cosmic acceleration traced by Type Ia supernovae
• Bayesian Calibrated Significance Levels Applied to the Spectral Tilt and Hemispherical Asymmetry
• Broken Isotropy from a Linear Modulation of the Primordial Perturbations
• The Signature of Proper Motion in the Microwave Sky
• Non-isotropy in the CMB power spectrum in single field inflation
• On the significance of power asymmetries in Planck CMB data at all scales
• Statistical Isotropy of CMB Polarization Maps
• Large-scale anomalies in the cosmic microwave background as signatures of non-Gaussianity
• Inflationary power asymmetry from primordial domain walls
• CMB Hemispherical Asymmetry: Long Mode Modulation and non-Gaussianity
• Hemispherical Power Asymmetry from a Space-Dependent Component of the Adiabatic Power Spectrum
• Hemispherical Anomaly from Asymmetric Initial States
• Litmus Test for Cosmic Hemispherical Asymmetry in the Cosmic Microwave Background B-mode polarization
• Generating the cosmic microwave background power asymmetry with $g_{NL}$
• Imprint of Inhomogeneous and Anisotropic Primordial Power Spectrum on CMB Polarization
• Generating $\fnl$ at $\ell\lsim 60$
• Linking the BICEP2 result and the hemispherical power asymmetry through spatial variation of $r$
• Hemispherical asymmetry from an isotropy violating stochastic gravitational wave background
• Scale-dependent CMB power asymmetry from primordial speed of sound and a generalized $\delta$N formalism
• SCoPE: An efficient method of Cosmological Parameter Estimation
• Search for a direction in the forest of Lyman-$\alpha$
• Cosmological Power Spectrum in Non-commutative Space-time

Cited by in corpus (15)

• Is the Observable Universe Consistent with the Cosmological Principle?
• Observational Challenges for the Standard FLRW Model
• Explaining Cosmological Anisotropy: Evidence for Causal Horizons from CMB data
• Anisotropy in the all-sky distribution of galaxy morphological types
• Bayesian estimation of our local motion from the Planck-2018 CMB temperature map
• A measurement of the scale of homogeneity in the Early Universe
• A new method for testing isotropy with Shannon entropy
• Finding origins of CMB anomalies in the inflationary quantum fluctuations
• f(R) Gravity in an Ellipsoidal Universe
• Joint Bayesian analysis of large angular scale CMB temperature anomalies
• Primordial anisotropies from cosmic strings during inflation
• Primordial inhomogeneities from massive defects during inflation
• Ellipsoidal Universe and Cosmic Shear
• SIToolBox : A package for Bayesian estimation of the isotropy violation in the CMB sky
• Revisiting the CMB homogeneity scale: low multipoles removal effect and extragalactic foreground masking