HI Epoch of Reionization Arrays

TL;DR

This paper discusses the development of radio arrays like LEDA and HERA aimed at detecting the hydrogen 21cm line to study the IGM's thermal history during reionization, addressing challenges like foregrounds and calibration.

Contribution

It reviews recent observational limits and compares different array strategies for detecting the 21cm signal from the Epoch of Reionization.

Findings

Recent limits on line brightness constrain models of the IGM.

Array efforts like LEDA and HERA are advancing detection capabilities.

Calibration and foreground removal remain key challenges.

Abstract

There are few data available with which to constrain the thermal history of the intergalactic medium (IGM) following global recombination. Thus far, most constraints flow from analyses of the Cosmic Microwave Background and optical spectroscopy along a few lines of sight. However, direct study of the IGM in emission or absorption against the CMB via the 1S hyperfine transition of Hydrogen would enable broad characterization thermal history and source populations. New generations of radio arrays are in development to measure this line signature. Bright foreground emission and the complexity of instrument calibration models are significant hurdles. How to optimize these is uncertain, resulting in a diversity in approaches. We discuss recent limits on line brightness, array efforts including the new Large Aperture Experiment to Detect the Dark Ages (LEDA), and the next generation Hydrogen Reionization Array (HERA) concept.