Building models for extended radio sources: implications for Epoch of Reionisation science

TL;DR

This paper investigates how incomplete sky models of extended radio sources introduce biases in the Epoch of Reionisation power spectrum measurements, emphasizing the importance of array configuration and baseline coverage.

Contribution

It analyzes the impact of incomplete sky models on EoR measurements and evaluates the array configurations needed for current and future radio telescopes to minimize bias.

Findings

Short baseline coverage is crucial for accurate modeling.

Longer baselines improve information on extended sources.

Array size and baseline length affect EoR measurement accuracy.

Abstract

We test the hypothesis that limitations in the sky model used to calibrate an interferometric radio telescope, where the model contains extended radio sources, will generate bias in the Epoch of Reionisation (EoR) power spectrum. The information contained in a calibration model about the spatial and spectral structure of an extended source is incomplete because a radio telescope cannot sample all Fourier components. Application of an incomplete sky model to calibration of EoR data will imprint residual error in the data, which propagates forward to the EoR power spectrum. This limited information is studied in the context of current and future planned instruments and surveys at EoR frequencies, such as the Murchison Widefield Array (MWA), Giant Metrewave Radio Telescope (GMRT) and the Square Kilometre Array (SKA1-Low). For the MWA EoR experiment, we find that both the additional short baseline $uv$-coverage of the compact EoR array, and the additional long baselines provided by TGSS and planned MWA expansions, are required to obtain sufficient information on all relevant scales. For SKA1-Low, arrays with maximum baselines of 49~km and 65~km yield comparable performance at 50~MHz and 150~MHz, while 39~km, 14~km and 4~km arrays yield degraded performance.