The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We analyse a 154 MHz image made from a 12 h observation with the Murchison Widefield Array (MWA) to determine the noise contribution and behaviour of the source counts down to 30 mJy. The MWA image h...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal Article |
| Published: |
Oxford University Press
2016
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| Online Access: | http://hdl.handle.net/20.500.11937/19645 |
| _version_ | 1848750090456399872 |
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| author | Franzen, Thomas Jackson, Carole Offringa, A. Ekers, Ronald Wayth, Randall Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Deshpande, A. Gaensler, B. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kaplan, D. Lonsdale, C. McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Morgan, J. Oberoi, D. Ord, S. Prabu, T. Seymour, Nick Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Trott, Cathryn Webster, R. Williams, Andrew Williams, C. |
| author_facet | Franzen, Thomas Jackson, Carole Offringa, A. Ekers, Ronald Wayth, Randall Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Deshpande, A. Gaensler, B. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kaplan, D. Lonsdale, C. McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Morgan, J. Oberoi, D. Ord, S. Prabu, T. Seymour, Nick Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Trott, Cathryn Webster, R. Williams, Andrew Williams, C. |
| author_sort | Franzen, Thomas |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We analyse a 154 MHz image made from a 12 h observation with the Murchison Widefield Array (MWA) to determine the noise contribution and behaviour of the source counts down to 30 mJy. The MWA image has a bandwidth of 30.72 MHz, a field-of-view within the half-power contour of the primary beam of 570 deg2, a resolution of 2.3 arcmin and contains 13 458 sources above 5s. The rms noise in the centre of the image is 4-5 mJy beam-1. The MWA counts are in excellent agreement with counts from other instruments and are the most precise ever derived in the flux density range 30-200 mJy due to the sky area covered. Using the deepest available source count data, we find that the MWA image is affected by sidelobe confusion noise at the ˜3.5 mJy beam-1 level, due to incompletely peeled and out-of-image sources, and classical confusion becomes apparent at ˜1.7 mJy beam-1. This work highlights that (i) further improvements in ionospheric calibration and deconvolution imaging techniques would be required to probe to the classical confusion limit and (ii) the shape of low-frequency source counts, including any flattening towards lower flux densities, must be determined from deeper ˜150 MHz surveys as it cannot be directly inferred from higher frequency data. |
| first_indexed | 2025-11-14T07:31:18Z |
| format | Journal Article |
| id | curtin-20.500.11937-19645 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T07:31:18Z |
| publishDate | 2016 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-196452017-09-13T13:47:29Z The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses Franzen, Thomas Jackson, Carole Offringa, A. Ekers, Ronald Wayth, Randall Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Deshpande, A. Gaensler, B. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kaplan, D. Lonsdale, C. McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Morgan, J. Oberoi, D. Ord, S. Prabu, T. Seymour, Nick Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Trott, Cathryn Webster, R. Williams, Andrew Williams, C. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. We analyse a 154 MHz image made from a 12 h observation with the Murchison Widefield Array (MWA) to determine the noise contribution and behaviour of the source counts down to 30 mJy. The MWA image has a bandwidth of 30.72 MHz, a field-of-view within the half-power contour of the primary beam of 570 deg2, a resolution of 2.3 arcmin and contains 13 458 sources above 5s. The rms noise in the centre of the image is 4-5 mJy beam-1. The MWA counts are in excellent agreement with counts from other instruments and are the most precise ever derived in the flux density range 30-200 mJy due to the sky area covered. Using the deepest available source count data, we find that the MWA image is affected by sidelobe confusion noise at the ˜3.5 mJy beam-1 level, due to incompletely peeled and out-of-image sources, and classical confusion becomes apparent at ˜1.7 mJy beam-1. This work highlights that (i) further improvements in ionospheric calibration and deconvolution imaging techniques would be required to probe to the classical confusion limit and (ii) the shape of low-frequency source counts, including any flattening towards lower flux densities, must be determined from deeper ˜150 MHz surveys as it cannot be directly inferred from higher frequency data. 2016 Journal Article http://hdl.handle.net/20.500.11937/19645 10.1093/mnras/stw823 Oxford University Press fulltext |
| spellingShingle | Franzen, Thomas Jackson, Carole Offringa, A. Ekers, Ronald Wayth, Randall Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Deshpande, A. Gaensler, B. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kaplan, D. Lonsdale, C. McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Morgan, J. Oberoi, D. Ord, S. Prabu, T. Seymour, Nick Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Trott, Cathryn Webster, R. Williams, Andrew Williams, C. The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses |
| title | The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses |
| title_full | The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses |
| title_fullStr | The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses |
| title_full_unstemmed | The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses |
| title_short | The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses |
| title_sort | 154 mhz radio sky observed by the murchison widefield array: noise, confusion, and first source count analyses |
| url | http://hdl.handle.net/20.500.11937/19645 |