Direct Optimal Mapping for 21cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array

TL;DR

This paper presents an optimal mapping pipeline for 21cm cosmology using HERA data, enabling precise sky imaging and model comparison, with demonstrated feasibility and broad applicability.

Contribution

The paper introduces a maximum likelihood mapping method validated with HERA data, improving sky model discrimination and computational efficiency for wide-field interferometric arrays.

Findings

HERA data agree with GLEAM catalogs to <10%

The pipeline discriminates between different sky models

Feasible computation costs for large interferometric datasets

Abstract

Motivated by the desire for wide-field images with well-defined statistical properties for 21cm cosmology, we implement an optimal mapping pipeline that computes a maximum likelihood estimator for the sky using the interferometric measurement equation. We demonstrate this direct optimal mapping with data from the Hydrogen Epoch of Reionization (HERA) Phase I observations. After validating the pipeline with simulated data, we develop a maximum likelihood figure-of-merit for comparing four sky models at 166MHz with a bandwidth of 100kHz. The HERA data agree with the GLEAM catalogs to <10%. After subtracting the GLEAM point sources, the HERA data discriminate between the different continuum sky models, providing most support for the model of Byrne et al. 2021. We report the computation cost for mapping the HERA Phase I data and project the computation for the HERA 320-antenna data; both are feasible with a modern server. The algorithm is broadly applicable to other interferometers and is valid for wide-field and non-coplanar arrays.