Zonal Modes of Cosmic Microwave Background Temperature Maps

TL;DR

This paper investigates the zonal modes (m=0) of the cosmic microwave background temperature maps to identify potential systematics and errors in foreground subtraction, using statistical analysis of low-l modes from WMAP data.

Contribution

It introduces a simple statistical method to analyze zonal modes as diagnostics for systematics in CMB maps derived from WMAP data.

Findings

Zonal modes reveal potential systematics in CMB maps.

Different cleaning procedures affect the behavior of low-l zonal modes.

Zonal modes serve as effective diagnostics for foreground subtraction errors.

Abstract

All-sky maps of the cosmic microwave background temperature fluctuations are usually represented by a spherical harmonic decomposition involving modes labelled by their degree l and order m (where -l < m < +l). The zonal modes (i.e those with m = 0) are of particular interest because they vary only with galactic latitude; any anomalous behaviour in them might therefore be an indication of erroneous foreground substraction. We perform a simple statistical analysis of the modes with low l for sky maps derived via different cleaning procedures from the Wilkinson Microwave Anisotropy Probe (WMAP) and show that the zonal modes provide a useful diagnostic of possible systematics.