Enhancing EoR limits through improved instrumental calibration of the MWA
Barry, Nichole Amanda
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Epoch of Reionization observations have the potential to be transformative in the field of cosmology, but this is impossible without unprecedented levels of precision in calibration. We enhance EoR upper limits from the Murchison Widefield Array through the improvement of instrumental calibration with in situ simulations. The reduced limit is a direct result of development in our pipeline, consisting of FHD and εppsilon, and highlights the precision and accuracy that we must achieve in calibration. We describe our pipeline in detail, including analysis of instrumental effects like pointings, cables, and polyphase filter banks. We perform experimental assessment of various sky-calibration approaches to the bandpass, and we characterize bit errors, phase response, and new techniques. An in situ calibration simulation verifies our experimental findings, and identifies the fundamental limits of sky-based calibration. We set a precedent for required bandpass accuracy to one part in 10<sup>5</sup>. Various improvements also contribute to our final limit, including beam kernel corrections and anti-aliasing filters found through signal loss simulations using our in situ framework. Our improved EoR upper limit is 6.75×10<sup>3</sup> mK<sup>2</sup> at <i>k</i> = 0.2 <i>h</i> Mpc<sup>-1</sup> for <i>z</i> = 7, an improvement of a factor of 4.0 over a previous analysis using the exact same data set. Techniques and infrastructure created in this work will influence future pipeline advances.
- Physics