Extracting the signal of cosmic string wakes from 21-cm 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 ΛCDM 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 the 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 that is promising in order to extract the signal, and we find that, having in mind a telescope with specifications similar to that of the MWA instrument, the string signal can be successfully extracted for a value of the string tension of Gμ=3×10-7. Prospects for further improvements of the analysis are discussed.