21 cm Angular Spectrum of Cosmic String Loops

TL;DR

This paper investigates the 21 cm signals caused by cosmic string loops, showing they can produce detectable brightness temperatures and dominate primordial fluctuation spectra under certain conditions, with potential detection by future SKA observations.

Contribution

It analytically evaluates the 21 cm brightness temperature and angular power spectrum from cosmic string loops, highlighting their potential observability.

Findings

Brightness temperature can reach 200 mK for current upper limit tension.

Angular power spectrum can dominate primordial fluctuations for certain tensions.

Future SKA-like observations could detect signals from loops with Gμ=10^{-8}.

Abstract

The 21 cm signatures induced by moving cosmic string loops are investigated. Moving cosmic string loops seed filamentary nonlinear objects. We analytically evaluate the differential 21 cm brightness temperature from these objects. We show that the brightness temperature reaches 200 mK for a loop whose tension is about the current upper limit, $G\mu\sim10^{-7}$. We also calculate the angular power spectrum, assuming scaling in loop distribution. We find that the angular power spectrum for $G\mu>10^{-8}$ at $z=30$ or $G\mu>10^{-10}$ at $z=20$ can dominate the spectrum of the primordial density fluctuations. Finally we show that a future SKA-like observation has the potential to detect the power spectrum due to loops with $G\mu=10^{-8}$ at $z=20$.