A study of fundamental limitations to statistical detection of redshifted HI from the epoch of reionization

TL;DR

This paper analyzes the fundamental uncertainties affecting the detection of redshifted HI signals from the Epoch of Reionization, focusing on foregrounds, thermal noise, and sample variance, and evaluates the MWA's sensitivity.

Contribution

It introduces a unified framework to estimate the impact of various uncertainties on EoR HI power spectrum detection and assesses the MWA's observational capabilities.

Findings

Detection feasible with 1000 hours of observation using MWA

Foreground contamination can be mitigated with bandpass shaping

Observing multiple fields offers no advantage over single field when thermal noise dominates

Abstract

In this paper we explore for the first time the relative magnitudes of three fundamental sources of uncertainty, namely, foreground contamination, thermal noise and sample variance in detecting the HI power spectrum from the Epoch of Reionization (EoR). We derive limits on the sensitivity of a Fourier synthesis telescope to detect EoR based on its array configuration and a statistical representation of images made by the instrument. We use the Murchison Widefield Array (MWA) configuration for our studies. Using a unified framework for estimating signal and noise components in the HI power spectrum, we derive an expression for and estimate the contamination from extragalactic point-like sources in three-dimensional k-space. Sensitivity for EoR HI power spectrum detection is estimated for different observing modes with MWA. With 1000 hours of observing on a single field using the 128-tile MWA, EoR detection is feasible (S/N > 1 for $k\lesssim 0.8$ Mpc$^{-1}$). Bandpass shaping and refinements to the EoR window are found to be effective in containing foreground contamination, which makes the instrument tolerant to imaging errors. We find that for a given observing time, observing many independent fields of view does not offer an advantage over a single field observation when thermal noise dominates over other uncertainties in the derived power spectrum.