Detection of cosmic structures using the bispectrum phase. II. First results from application to cosmic reionization using the Hydrogen Epoch of Reionization Array

Abstract

Characterizing the epoch of reionization (EoR) at z ≳ 6 via the redshifted 21 cm line of neutral Hydrogen (H I) is critical to modern astrophysics and cosmology, and thus a key science goal of many current and planned low-frequency radio telescopes. The primary challenge to detecting this signal is the overwhelmingly bright foreground emission at these frequencies, placing stringent requirements on the knowledge of the instruments and inaccuracies in analyses. Results from these experiments have largely been limited not by thermal sensitivity but by systematics, particularly caused by the inability to calibrate the instrument to high accuracy. The interferometric bispectrum phase is immune to antenna-based calibration and errors therein, and presents an independent alternative to detect the EoR H I fluctuations while largely avoiding *

Statistical recovery of the BAO scale from multipoles of the beam-convolved 21cm correlation function

“…The beam function is convolved with the observed intensity field and produces a frequency-dependent smoothing effect that not only dampens features at or below the scale of the beam size, but also modulates the foregrounds, resulting in foreground power being scattered to Fourier modes at much higher wavenumbers (Santos et al 2004;Jelić et al 2008;Chapman et al 2012;Liu et al 2014;Villaescusa-Navarro et al 2017;Asad et al 2019;Matshawule et al 2020;Choudhuri et al 2020;Hothi et al 2020). Nevertheless, advances in calibration and signal filtering are gradually improving measurements to the point that positive detections of the cosmological 21cm signal are anticipated in the coming years without the need for cross-correlation (McKinley et al 2018;Wang et al 2020;Thyagarajan et al 2020).…”

Investigating X-ray sources during the epoch of reionization with the 21 cm signal

“…Although also LOFAR, MWA, and HERA might be able to measure the 21 cm power spectra and bispectra (e.g. Shimabukuro et al 2017;Thyagarajan et al 2020), as they reach the maximum sensitivity for an angular resolution which is not covered by the box size of our simulations, we do not present any results for these telescopes.…”

First Results from HERA Phase I: Upper Limits on the Epoch of Reionization 21 cm Power Spectrum

“…This shows that the full process of measuring the sky brightness, including the instrument itself and our analysis pipeline, achieves a dynamic range of 10 9 in power between the peak foreground emission and the thermal noise floor at high k, which is a necessary but not quite sufficient criterion for an eventual 21 cm signal detection. Note that a complementary analysis of Phase I data using the bispectrum phase also achieve a dynamic range of 10 8 between peak foreground power and the recovered noise floor (Thyagarajan et al 2020), but used less data than what is presented here.…”

“…), and pipeline validation (Aguirre et al in prep.). Complementary studies on the data set discussed in this work also include foreground modeling (Ghosh et al 2020), imaging (Carilli et al 2018), power spectrum analysis of the bispectrum phase (Thyagarajan et al 2020), antenna primary beam characterization (Nunhokee et al 2017), and electromagnetic modeling of the front-end signal chain (Fagnoni et al 2021). Here, we give an overview of the full analysis pipeline, discuss the criteria used for data selection, present the power spectrum limits, and describe statistical tests used to characterize the performance of the system and our analysis techniques.…”