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Extrapolating Radio Sources to Low Frequencies using the GLEAM Catalog

Presentation #240.03 in the session Catalogs — iPoster Session.

Published onJun 29, 2022
Extrapolating Radio Sources to Low Frequencies using the GLEAM Catalog

Observing HI from the Epoch of Reionization requires modeling of radio sources across a wide range of frequencies. We use the GaLactic and Extragalactic All-sky MWA Survey (GLEAM) radio source catalog, produced by the Murchison Widefield Array (MWA) which has a frequency range of 76-227 MHz. Our work with GLEAM focuses on extrapolating source spectra down to lower frequencies that cover the full observation band of Hydrogen Epoch of Reionization Array (HERA), so that GLEAM sources can be used to calibrate HERA data. We perform power-law source fitting, preferencing lower frequencies included in GLEAM, in order to find fits that more accurately describe the low frequency end of the catalog. This enables us to extrapolate fits to frequencies below GLEAM’s range. We implement a multi-tiered log linear fitting approach similar to the one used in the fits reported by GLEAM, using the reduced X2 to evaluate goodness of fit. We fit iteratively, re-fitting on only a subset of low frequencies when a fit on all frequencies is poor. Following manual inspection of a large number of source fits, focusing on outlier sources and fits with abnormally large reduced X2, we find that our fitting algorithm consistently performs as expected.

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