The Effects of Polarized Foregrounds on 21cm Epoch of Reionization Power Spectrum Measurements

TL;DR

This paper investigates how Faraday-rotated polarized foreground emission can contaminate 21cm EoR power spectrum measurements, showing that leakage could significantly exceed the expected signal, thus impacting detection efforts.

Contribution

It provides a simulation-based analysis of polarized foreground leakage into 21cm EoR measurements using the delay spectrum method, highlighting potential contamination levels.

Findings

Leakage into the unpolarized power spectrum can be several orders of magnitude above the EoR signal.

Faraday rotation introduces spectral structures that complicate foreground removal.

Simulations suggest polarization leakage is a critical factor for EoR experiments.

Abstract

Experiments aimed at detecting highly-redshifted 21 centimeter emission from the Epoch of Reionization (EoR) are plagued by the contamination of foreground emission. A potentially important source of contaminating foregrounds may be Faraday-rotated, polarized emission, which leaks into the estimate of the intrinsically unpolarized EoR signal. While these foregrounds' intrinsic polarization may not be problematic, the spectral structure introduced by the Faraday rotation could be. To better understand and characterize these effects, we present a simulation of the polarized sky between 120 and 180 MHz. We compute a single visibility, and estimate the three-dimensional power spectrum from that visibility using the delay spectrum approach presented in Parsons et al. (2012b) . Using the Donald C. Backer Precision Array to Probe the Epoch of Reionization (PAPER) as an example instrument, we show the expected leakage into the unpolarized power spectrum to be several orders of magnitude above the expected 21cm EoR signal.