Probing IGM Physics during Cosmic Dawn using the Redshifted 21-cm Bispectrum

TL;DR

This paper demonstrates that analyzing the redshift evolution of the 21-cm bispectrum can distinguish between Lyα coupling and X-ray heating effects in the IGM during Cosmic Dawn, offering a new method to study early universe physics.

Contribution

The study introduces a novel approach using the 21-cm bispectrum evolution to separately probe Lyα coupling and X-ray heating during Cosmic Dawn.

Findings

Bispectrum sign and magnitude evolve distinctly with redshift.

Simulation results show potential to disentangle IGM heating and coupling processes.

Provides a new observational tool for early universe studies.

Abstract

With the advent of the first luminous sources at Cosmic Dawn (CD), the redshifted 21-cm signal, from the neutral hydrogen in the Inter-Galactic Medium (IGM), is predicted to undergo a transition from absorption to emission against the CMB. Using simulations, we show that the redshift evolution of the sign and the magnitude of the 21-cm bispectrum can disentangle the contributions from Ly$\alpha$ coupling and X-ray heating of the IGM, the two most dominant processes which drive this transition. This opens a new avenue to probe the first luminous sources and the IGM physics at CD.