Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation
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 d...
| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Journal Article |
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Oxford University Press
2018
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| Online Access: | http://purl.org/au-research/grants/arc/DE160100849 http://hdl.handle.net/20.500.11937/74070 |
| _version_ | 1848763172095262720 |
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| author | McKinley, B. Bernardi, G. Trott, Cathryn Line, J. Wayth, Randall Offringa, A. Pindor, B. Jordan, Christopher Sokolowski, Marcin Tingay, Steven Lenc, E. Hurley-Walker, Natasha Bowman, J. Briggs, F. Webster, R. |
| author_facet | McKinley, B. Bernardi, G. Trott, Cathryn Line, J. Wayth, Randall Offringa, A. Pindor, B. Jordan, Christopher Sokolowski, Marcin Tingay, Steven Lenc, E. Hurley-Walker, Natasha Bowman, J. Briggs, F. Webster, R. |
| author_sort | McKinley, B. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | 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. |
| first_indexed | 2025-11-14T10:59:14Z |
| format | Journal Article |
| id | curtin-20.500.11937-74070 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T10:59:14Z |
| publishDate | 2018 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-740702022-10-06T03:40:49Z Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation McKinley, B. Bernardi, G. Trott, Cathryn Line, J. Wayth, Randall Offringa, A. Pindor, B. Jordan, Christopher Sokolowski, Marcin Tingay, Steven Lenc, E. Hurley-Walker, Natasha Bowman, J. Briggs, F. Webster, R. 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. 2018 Journal Article http://hdl.handle.net/20.500.11937/74070 10.1093/MNRAS/STY2437 http://purl.org/au-research/grants/arc/DE160100849 http://purl.org/au-research/grants/arc/DE140100316 Oxford University Press fulltext |
| spellingShingle | McKinley, B. Bernardi, G. Trott, Cathryn Line, J. Wayth, Randall Offringa, A. Pindor, B. Jordan, Christopher Sokolowski, Marcin Tingay, Steven Lenc, E. Hurley-Walker, Natasha Bowman, J. Briggs, F. Webster, R. Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation |
| title | Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation |
| title_full | Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation |
| title_fullStr | Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation |
| title_full_unstemmed | Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation |
| title_short | Measuring the global 21-cm signal with the MWA-I: Improved measurements of the Galactic synchrotron background using lunar occultation |
| title_sort | measuring the global 21-cm signal with the mwa-i: improved measurements of the galactic synchrotron background using lunar occultation |
| url | http://purl.org/au-research/grants/arc/DE160100849 http://purl.org/au-research/grants/arc/DE160100849 http://hdl.handle.net/20.500.11937/74070 |