Local variance asymmetries in Planck temperature anisotropy maps

TL;DR

This paper extends the analysis of local variance asymmetries in Planck temperature maps to smaller scales, demonstrating the ability to measure the Doppler dipole and confirming large-scale hemispherical power asymmetry.

Contribution

It introduces a method to analyze local variance asymmetries at smaller scales and measures the Doppler dipole using Planck data, enhancing previous large-scale studies.

Findings

Doppler dipole can be measured at 3 sigma significance after removing large-scale features.

No additional power asymmetry found at small scales beyond cosmic variance.

Large-scale hemispherical power asymmetry confirmed at over 3.3 sigma.

Abstract

Recently, it was shown that local variance maps of temperature anisotropy are simple and useful tools for the study of large scale hemispherical power asymmetry. This was done by studying the distribution of dipoles of the local variance maps. In this work, we extend the study of the dipolar asymmetry in local variance maps using foreground cleaned Planck 143 GHz and 217 GHz data to smaller scales. In doing so, we include the effect of the CMB Doppler dipole. Further, we show that it is possible to use local variance maps to measure the Doppler dipole in these Planck channel maps, after removing large scale features (up to $l=600$), at a significance of about $3 \sigma$. At these small scales, we do not find any power asymmetry in the direction of the anomalous large scale power asymmetry beyond that expected from cosmic variance. At large scales, we verify previous results i.e. the presence of hemispherical power asymmetry at a significance of at least $3.3 \sigma$.