Calibration Requirements for Detecting the 21 cm Epoch of Reionization Power Spectrum and Implications for the SKA

TL;DR

This paper demonstrates through simulations that traditional sky-based calibration methods introduce contamination in 21 cm EoR power spectrum measurements unless calibration models are unrealistically precise, impacting future instrument design.

Contribution

It provides a comprehensive simulation framework revealing calibration limitations and their impact on EoR measurements, highlighting the need for improved calibration strategies.

Findings

Sky-based calibration can cause contamination in power spectrum modes.

Calibration accuracy is limited by catalog completeness and antenna spectral smoothness.

Implications for SKA design include stricter calibration requirements.

Abstract

21 cm Epoch of Reionization observations promise to transform our understanding of galaxy formation, but these observations are impossible without unprecedented levels of instrument calibration. We present end-to-end simulations of a full EoR power spectrum analysis including all of the major components of a real data processing pipeline: models of astrophysical foregrounds and EoR signal, frequency-dependent instrument effects, sky-based antenna calibration, and the full PS analysis. This study reveals that traditional sky-based per-frequency antenna calibration can only be implemented in EoR measurement analyses if the calibration model is unrealistically accurate. For reasonable levels of catalog completeness, the calibration introduces contamination in otherwise foreground-free power spectrum modes, precluding a PS measurement. We explore the origin of this contamination and potential mitigation techniques. We show that there is a strong joint constraint on the precision of the calibration catalog and the inherent spectral smoothness of antennae, and that this has significant implications for the instrumental design of the SKA and other future EoR observatories.