Measuring Baryon Acoustic Oscillations on 21 cm intensity fluctuations at moderate redshifts

TL;DR

This paper explores the potential of 21 cm intensity mapping with ground-based radio interferometers to measure baryon acoustic oscillations at moderate redshifts, aiming to constrain dark energy properties.

Contribution

It analyzes systematic and statistical errors in acoustic scale estimation using simulations, and evaluates the observational strategies and capabilities of future hydrogen surveys.

Findings

10 interferometers with 300 dishes each can detect acoustic features within a few years.

Fourier-space foreground subtraction techniques are effective in simulations.

Wide field-of-view and multi-beam observations enhance measurement prospects.

Abstract

After reionization, emission in the 21 cm hyperfine transition provides a direct probe of neutral hydrogen distributed in galaxies. Different from galaxy redshift surveys, observation of baryon acoustic oscillations in the cumulative 21 cm emission may offer an attractive method for constraining dark energy properties at moderate redshifts. Keys to this program are techniques to extract the faint cosmological signal from various contaminants, such as detector noise and continuum foregrounds. In this paper, we investigate the possible systematic and statistical errors in the acoustic scale estimates using ground-based radio interferometers. Based on the simulated 21 cm interferometric measurements, we analyze the performance of a Fourier-space, light-of-sight algorithm in subtracting foregrounds, and further study the observing strategy as a function of instrumental configurations. Measurement uncertainties are presented from a suite of simulations with a variety of parameters, in order to have an estimate of what behaviors will be accessible in the future generation of hydrogen surveys. We find that 10 separate interferometers, each of which contains $\sim 300$ dishes, observes an independent patch of the sky and produces an instantaneous field-of-view of $\sim 100$ $\rm deg^2$, can be used to make a significant detection of acoustic features over a period of a few years. Compared to optical surveys, the broad bandwidth, wide field-of-view and multi-beam observation are all unprecedented capabilities of low-frequency radio experiments.