Research and Development for HI Intensity Mapping

TL;DR

This paper reviews the progress and challenges in developing hardware, data analysis, and simulation techniques for HI intensity mapping using large radio arrays, highlighting technical issues and future prospects.

Contribution

It provides a comprehensive overview of the technical hurdles and recent advances in HI intensity mapping, emphasizing the potential for scientific discoveries across cosmic history.

Findings

Technical issues are solvable with further development.

Advances enable studies from early galaxy formation to dark energy.

Calibration and analysis remain key challenges.

Abstract

Development of the hardware, data analysis, and simulation techniques for large compact radio arrays dedicated to mapping the 21 cm line of neutral hydrogen gas has proven to be more difficult than imagined twenty years ago when such telescopes were first proposed. Despite tremendous technical and methodological advances, there are several outstanding questions on how to optimally calibrate and analyze such data. On the positive side, it has become clear that the outstanding issues are purely technical in nature and can be solved with sufficient development activity. Such activity will enable science across redshifts, from early galaxy evolution in the pre-reionization era to dark energy evolution at low redshift.