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This paper presents the design and deployment of the Hydrogen Epoch of Reionization Array (HERA) phase II system. HERA is designed as a staged experiment targeting 21 cm emission measurements of the Epoch of Reionization. First results from the phase I array are published as of early 2022, and deployment of the phase II system is nearing completion. We describe the design of the phase II system and discuss progress on commissioning and future upgrades. As HERA is a designated Square Kilometre Array pathfinder instrument, we also show a number of “case studies” that investigate systematics seen while commissioning the phase II system, which may be of use in the design and operation of future arrays. Common pathologies are likely to manifest in similar ways across instruments, and many of these sources of contamination can be mitigated once the source is identified.

In order to study the "Cosmic Dawn" and the Epoch of Reionization with 21 cm tomography, we need to statistically separate the cosmological signal from foregrounds known to be orders of magnitude brighter. Over the last few years, we have learned much about the role our telescopes play in creating a putatively foreground-free region called the "EoR window." In this work, we examine how an interferometer's effects can be taken into account in a way that allows for the rigorous estimation of 21 cm power spectra from interferometric maps while mitigating foreground contamination and thus increasing sensitivity. This requires a precise understanding of the statistical relationship between the maps we make and the underlying true sky. While some of these calculations would be computationally infeasible if performed exactly, we explore several well-controlled approximations that make mapmaking and the calculation of map statistics much faster, especially for compact and highly redundant interferometers designed specifically for 21 cm cosmology. We demonstrate the utility of these methods and the parametrized trade-offs between accuracy and speed using one such telescope, the upcoming Hydrogen Epoch of Reionization Array, as a case study. [ABSTRACT FROM AUTHOR]

Nearly all patients with tuberous sclerosis complex (TSC) develop renal angiomyolipomas, although the tumor cell of origin is unknown. We observed decreased renal angiomyolipoma development in patients with TSC2- polycystic kidney disease 1deletion syndrome and hypertension that were treated from an early age with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers compared with patients who did not receive this therapy. TSC-associated renal angiomyolipomas expressed ANG II type 1 receptors, platelet-derived growth factor receptor-β, desmin, α-smooth muscle actin, and VEGF receptor 2 but did not express the adipocyte marker S100 or the endothelial marker CD31. Sera of TSC patients exhibited increased vascular mural cell-secreted peptides, such as VEGF-A, VEGF-D, soluble VEGF receptor 2, and collagen type IV. These findings suggest that angiomyolipomas may arise from renal pericytes. ANG II treatment of angiomyolipoma cells in vitro resulted in an exaggerated intracellular Ca2+response and increased proliferation, which were blocked by the ANG II type 2 receptor antagonist valsartan. Blockade of ANG II signaling may have preventative therapeutic potential for angiomyolipomas.

We present techniques for bridging the gap between idealized inverse covariance weighted quadratic estimation of 21 cm power spectra and the real-world challenges presented universally by interferometric observation. By carefully evaluating various estimators and adapting our techniques for large but incom-plete data sets, we develop a robust power spectrum estimation framework that preserves the so-called "Epoch of Reionization (EoR) window" and keeps track of estimator errors and covariances. We apply our method to observations from the 32-tile prototype of the Murchinson Widefield Array to demonstrate the importance of a judicious analysis technique. Lastly, we apply our method to investigate the depend-ence of the clean EoR window on frequency--especially the frequency dependence of the so-called "wedge" feature--and establish upper limits on the power spectrum from z = 6.2 to z = 11.7. Our lowest limit is Δ(k) < 0.3 Kelvin at 95% confidence at a comoving scale k = 0.046 Mpc-1 and z = 9.5. [ABSTRACT FROM AUTHOR]

We develop and demonstrate an acceleration of the Liu and Tegmark quadratic estimator formalism for inverse variance foreground subtraction and power spectrum estimation in 21 cm tomography from φ(N3) to φ(N logN), where TV is the number of voxels of data. This technique makes feasible the megavoxel scale analysis necessary for current and upcoming radio interferometers by making only moderately restrictive assumptions about foreground models and survey geometry. We exploit iterative and Monte Carlo techniques and the symmetries of the foreground covariance matrices to quickly estimate the 21 cm brightness temperature power spectrum, P(k, k), the Fisher information matrix, the error bars, the window functions, and the bias. We also extend the Liu and Tegmark foreground model to include bright point sources with known positions in a way that scales as φ[(NlogN) × (N point sources)] ⩽ φ(N5/2). As a first application of our method, we forecast error bars and window functions for the upcoming 128-tile deployment of the Murchinson Widefield Array, showing that 1000 hours of observation should prove sufficiently sensitive to detect the power spectrum signal from the Epoch of Reionization. [ABSTRACT FROM AUTHOR]

We present a framework for identifying and flagging malfunctioning antennas in large radio interferometers. We outline two distinct categories of metrics designed to detect outliers along known failure modes of large arrays: cross‐correlation metrics, based on all antenna pairs, and auto‐correlation metrics, based solely on individual antennas. We define and motivate the statistical framework for all metrics used, and present tailored visualizations that aid us in clearly identifying new and existing systematics. We implement these techniques using data from 105 antennas in the Hydrogen Epoch of Reionization Array (HERA) as a case study. Finally, we provide a detailed algorithm for implementing these metrics as flagging tools on real data sets. Monitoring the performance of a many‐element system is essential to acquiring science‐quality data and requires an automated approachWe define metrics based on cross‐correlations that assess the health of the whole array and its component subsystems in an automated wayWe outline metrics based on autocorrelations that identify systematics and provide a generalizable approach to automated antenna flagging Monitoring the performance of a many‐element system is essential to acquiring science‐quality data and requires an automated approach We define metrics based on cross‐correlations that assess the health of the whole array and its component subsystems in an automated way We outline metrics based on autocorrelations that identify systematics and provide a generalizable approach to automated antenna flagging

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.