@article{c92e843cb3ba4020961c9e2aba8f6603,
title = "Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation",
abstract = "We present early results from a project to measure the sky-averaged (global), redshifted 21 cm signal from the Epoch of Reionization (EoR), using the Murchison Widefield Array (MWA) telescope. Because interferometers are not sensitive to a spatially invariant global average, they cannot be used to detect this signal using standard techniques.However, lunar occultation of the radio sky imprints a spatial structure on the global signal, allowing us to measure the average brightness temperature of the patch of sky immediately surrounding the Moon. In this paper, we present one night of Moon observations with the MWA between 72-230 MHz and verify our techniques to extract the background sky temperature from measurements of the Moon's flux density. We improve upon previous work using the lunar occultation technique by using a more sophisticated model for reflected 'earthshine' and by employing image differencing to remove imaging artefacts. We leave the Moon's (constant) radio brightness temperature as a free parameter in our fit to the data and as a result, measure Tmoon = 180 ± 12 K and a Galactic synchrotron spectral index of -2.64 ± 0.14, at the position of the Moon. Finally, we evaluate the prospects of the lunar occultation technique for a global EoR detection and map out a way forward for future work with the MWA.",
keywords = "Dark ages, First stars, Moon, Reionization, Techniques: interferometric",
author = "B. McKinley and G. Bernardi and Trott, {C. M.} and Line, {J. L.B.} and Wayth, {R. B.} and Offringa, {A. R.} and B. Pindor and Jordan, {C. H.} and M. Sokolowski and Tingay, {S. J.} and E. Lenc and N. Hurley-Walker and Judd Bowman and F. Briggs and Webster, {R. L.}",
note = "Funding Information: This scientific work makes use of the Murchison Radio-astronomy Observatory, operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. Support for the operation of the MWA is provided by the Australian Government (National Collaborative Research Infrastructure Strategy), under a contract to Curtin University administered by Astronomy Australia Limited. The authors would like to thank the anonymous referee for their useful comments and suggestions that improved the paper. We acknowledge the Pawsey Supercomputing Centre, which is supported by the Western Australian and Australian Governments. BM is funded by a Discovery Early Career Researcher grant from the Australian Research Council (project number DE160100849). We acknowledge that the Bentley campus of the Curtin University of Technology, upon which most of this paper was written, is located on the land of the Noongar people. The Centre for All-Sky Astrophysics (CAASTRO) is an Australian Research Council Centre of Excellence, funded by grant CE110001020. Parts of this research were supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. CMT is supported under the Australian Research Council{\textquoteright}s Discovery Early Career Researcher funding scheme (project number DE140100316). GB acknowledges support from the Royal Society and the Newton Fund under grant NA150184. This work is based on the research supported in part by the National Research Foundation of South Africa (grant No. 103424). Publisher Copyright: {\textcopyright} 2018 The Author(s).",
year = "2018",
month = dec,
day = "1",
doi = "10.1093/MNRAS/STY2437",
language = "English (US)",
volume = "481",
pages = "5034--5045",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "4",
}