Four Fundamental Foreground Power Spectrum Shapes for 21 cm Cosmology Observations

TL;DR

This paper identifies four fundamental foreground power spectrum shapes caused by mode-mixing in 21 cm cosmology, explaining observed contamination structures and aiding in calibration and foreground subtraction for future Epoch of Reionization and BAO measurements.

Contribution

It introduces a novel classification of mode-mixing contamination shapes and explains the wedge structure in 21 cm power spectra, improving understanding of foreground effects.

Findings

Four fundamental power spectrum shapes identified

Explanation of wedge-like contamination structure

Forecast of a mostly contamination-free EoR window

Abstract

Contamination from instrumental effects interacting with bright astrophysical sources is the primary impediment to measuring Epoch of Reionization and BAO 21 cm power spectra---an effect called mode-mixing. In this paper we identify four fundamental power spectrum shapes produced by mode-mixing that will affect all upcoming observations. We are able, for the first time, to explain the wedge-like structure seen in advanced simulations and to forecast the shape of an 'EoR window' that is mostly free of contamination. Understanding the origins of these contaminations also enables us to identify calibration and foreground subtraction errors below the imaging limit, providing a powerful new tool for precision observations.