Extracting the Signal of Cosmic String Wakes from 21-cm Observations

TL;DR

This paper investigates methods to detect cosmic string wakes in 21-cm intensity maps, demonstrating that a specific three-point statistic can successfully extract the string signal from noisy data, especially with instruments like MWA.

Contribution

It introduces a novel three-point statistic tailored to the geometry of cosmic string signals, enabling their extraction from noisy 21-cm interferometric data.

Findings

Successful extraction of cosmic string signals at Gμ=3×10⁻⁷ with MWA-like instruments.

Foreground subtraction is feasible due to the narrow redshift feature of the string signal.

The proposed method enhances prospects for detecting cosmic strings in future observations.

Abstract

A cosmic string wake produces a distinct non-Gaussian signal in 21-cm intensity maps at redshifts above that of reionization. While the string signal is (locally) larger in amplitude than the signal of the Gaussian fluctuations of the $\Lambda$CDM model, they are overwhelmed (even locally in position space) by astrophysical and instrumental foregrounds. Here, we study to what extent the signal can be extracted from noisy interferometric data. The narrowness of the string-induced feature in redshift direction allows for a subtraction of astrophysical and instrumental foregrounds. Based on the specific geometry of the string signal we identify a particular three-point statistic which is promising in order to extract the signal, and we find that, having in mind a telescope of specifications similar to that of the MWA instrument, the string signal can be successfully extracted for a value of the string tension of $G\mu = 3 \times 10^{-7}$. Prospects for further improvements of the analysis are discussed.