Model Independent Foreground Power Spectrum Estimation using WMAP 5-year Data

TL;DR

This paper introduces a model independent method to estimate galactic foreground power spectra from WMAP 5-year data, avoiding template assumptions and analyzing spectral index variations across the sky.

Contribution

It extends previous CMB power spectrum estimation techniques to foregrounds, providing a new harmonic basis approach and comparative analysis with MEM maps.

Findings

MEM maps overestimate foreground power near the galactic plane

MEM maps underestimate foreground power at high latitudes

The method reveals spatial variation in synchrotron spectral index

Abstract

In this paper, we propose & implement on WMAP 5-year data, a model independent approach of foreground power spectrum estimation for multifrequency observations of CMB experiments. Recently a model independent approach of CMB power spectrum estimation was proposed by Saha et al. 2006. This methodology demonstrates that CMB power spectrum can be reliably estimated solely from WMAP data without assuming any template models for the foreground components. In the current paper, we extend this work to estimate the galactic foreground power spectrum using the WMAP 5 year maps following a self contained analysis. We apply the model independent method in harmonic basis to estimate the foreground power spectrum and frequency dependence of combined foregrounds. We also study the behaviour of synchrotron spectral index variation over different regions of the sky. We compare our results with those obtained from MEM foreground maps which are formed in pixel space. We find that relative to our model independent estimates MEM maps overestimates the foreground power close to galactic plane and underestimates it at high latitudes.