Hydrogen Epoch of Reionization Array (HERA)

Abstract

The Hydrogen Epoch of Reionization Array (HERA) is a staged experiment to measure 21 cm emission from the primordial intergalactic medium (IGM) throughout cosmic reionization (z=6-12), and to explore earlier epochs of our Cosmic Dawn (z∼30). During these epochs, early stars and black holes heated and ionized the IGM, introducing fluctuations in 21 cm emission. HERA is designed to characterize the evolution of the 21 cm power spectrum to constrain the timing and morphology of reionization, the properties of the first galaxies, the evolution of large-scale structure, and the early sources of heating. The full HERA instrument will be a 350-element interferometer in South Africa consisting of 14 m parabolic dishes observing from 50 to 250 MHz. Currently, 19 dishes have been deployed on site and the next 18 are under construction. HERA has been designated as an SKA Precursor instrument. In this paper, we summarize HERA's scientific context and provide forecasts for its key science results. After reviewing the current state of the art in foreground mitigation, we use the delay-spectrum technique to motivate high-level performance requirements for the HERA instrument. Next, we present the HERA instrument design, along with the subsystem specifications that ensure that HERA meets its performance requirements. Finally, we summarize the schedule and status of the project. We conclude by suggesting that, given the realities of foreground contamination, current-generation 21 cm instruments are approaching their sensitivity limits. HERA is designed to bring both the sensitivity and the precision to deliver its primary science on the basis of proven foreground filtering techniques, while developing new subtraction techniques to unlock new capabilities. The result will be a major step toward realizing the widely recognized scientific potential of 21 cm cosmology.

Probing the small-scale matter power spectrum with large-scale 21-cm data

“…In this work we will focus on upcoming measurements of the 21-cm power spectrum from the hydrogen epoch of reionization array (HERA) [117], currently under construction in South Africa. A similar analysis could be carried out for other interferometers, such as the low-frequency array (LOFAR) [118], the longwavelength array (LWA) [119], or the square-kilometer array (SKA) [120].…”

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

“…Mesinger et al 2011). Mitigating all possible effects that could prevent a 21-cm signal detection is particularly important since these instruments are also pathfinders for the much more sensitive and ambitious second-generation instruments such as the SKA 7 (Koopmans et al 2015) and HERA 8 (DeBoer et al 2017).…”

Absolute Calibration Strategies for the Hydrogen Epoch of Reionization Array and Their Impact on the 21 cm Power Spectrum

“…The Hydrogen Epoch of Reionization Array 1 (HERA; DeBoer et al 2017) is a targeted, radio interferometric experiment that aims to measure the cosmological 21 cm spin-flip emission from primordial hydrogen in the intergalactic medium (IGM) at Cosmic Dawn. One of the last frontiers of cosmology and high redshift astrophysics, the Cosmic Dawn marks the era when the first stars, black holes, and galaxies formed and interacted with the surrounding IGM.…”