The precision and accuracy of early Epoch of Reionization foreground models: comparing MWA and PAPER 32-antenna source catalogs

TL;DR

This study compares early Epoch of Reionization source catalogs from MWA and PAPER, assessing their flux calibration accuracy and identifying primary sources of error to improve future EoR observations.

Contribution

It introduces a Bayesian MCMC method to compare flux scales and analyzes primary beam and CLEAN-related errors in EoR foreground models.

Findings

Flux scales agree within 20% between instruments

Differences mainly due to primary beam inaccuracies

Errors in bright sources linked to CLEAN deconvolution

Abstract

As observations of the Epoch of Reionization (EoR) in redshifted 21cm emission begin, we asses the accuracy of the early catalog results from the Precision Array for Probing the Epoch of Reionization (PAPER) and the Murchison Widefield Array. The MWA EoR approach derives much of its sensitivity from subtracting foregrounds to <1% precision while the PAPER approach relies on the stability and symmetry of the primary beam. Both require an accurate flux calibration to set the amplitude of the measured power spectrum. The two instruments are very similar in resolution, sensitivity, sky coverage and spectral range and have produced catalogs from nearly contemporaneous data. We use a Bayesian MCMC fitting method to estimate that the two instruments are on the same flux scale to within 20% and find that the images are mostly in good agreement. We then investigate the source of the errors by comparing two overlapping MWA facets where we find that the differences are primarily related to an inaccurate model of the primary beam but also correlated errors in bright sources due to CLEAN. We conclude with suggestions for mitigating and better characterizing these effects.