The Impact of Beam Variations on Power Spectrum Estimation for 21-cm Cosmology I: Simulations of Foreground Contamination for HERA

Abstract

Detecting cosmological signals from the Epoch of Reionization (EoR) requires high-precision calibration to isolate the cosmological signals from foreground emission. In radio interferometery, perturbed primary beams of antenna elements can disrupt the precise calibration, which results in contaminating the foreground-free region, or the EoR window, in the cylindrically averaged power spectrum. For Hydrogen Epoch of Reionization Array (HERA), we simulate and characterize the perturbed primary beams induced by feed motions such as axial, lateral, and tilting motions, above the 14-meter dish. To understand the effect of the perturbed beams, visibility measurements are modeled with two different foreground components, point sources and diffuse sources, and we find different feed motions present a different reaction to each type of sky source. HERA's redundant-baseline calibration in the presence of non-redundant antenna beams due to feed motions introduces chromatic errors in gain solutions, which produces foreground power leakage into the EoR window. The observed leakage from vertical feed motions comes predominately from point sources around zenith. Furthermore, the observed leakage from horizontal and tilting feed motion comes predominately from the diffuse components near the horizon. Mitigation of chromatic gain errors will be necessary for robust detection of the EoR signals with minimal foreground bias, and this will be discussed in the subsequent paper.

Accepted for publication in ApJ

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Cited by in corpus (6)

• Hydrogen Epoch of Reionization Array (HERA) Phase II Deployment and Commissioning
• Field-level Reconstruction from Foreground-Contaminated 21-cm Maps
• Exploring One-point Statistics in HERA Phase I Data: Effects of Foregrounds and Systematics on Measuring One-Point Statistics
• Primary Beam Chromaticity in HIRAX: I. Characterization from Simulations and Power Spectrum Implications
• The impact of lunar topography on the 21-cm power spectrum for grid-based arrays : Insights for the Dark-ages EXplorer (DEX)
• Mitigating gain calibration errors from EoR observations with SKA1-Low AA*