The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum
We have acquired radio-continuum data between 70 MHz and 48 GHz for a sample of 19 southern starburst galaxies at moderate redshifts (0.067 < z < 0.227) with the aim of separating synchrotron and free–free emission components. Using a Bayesian framework, we find the radio continuum is rarely c...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal Article |
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Oxford University Press
2018
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| Online Access: | http://hdl.handle.net/20.500.11937/66555 |
| _version_ | 1848761350751256576 |
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| author | Galvin, T. Seymour, Nick Marvil, J. Filipovic, M. Tothill, N. McDermid, R. Hurley-Walker, Natasha Hancock, Paul Callingham, J. Cook, R. Norris, R. Bell, M. Dwarakanath, K. For, B. Gaensler, B. Hindson, L. Johnston-Hollitt, Melanie Kapinska, A. Lenc, E. McKinley, B. Morgan, John Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. |
| author_facet | Galvin, T. Seymour, Nick Marvil, J. Filipovic, M. Tothill, N. McDermid, R. Hurley-Walker, Natasha Hancock, Paul Callingham, J. Cook, R. Norris, R. Bell, M. Dwarakanath, K. For, B. Gaensler, B. Hindson, L. Johnston-Hollitt, Melanie Kapinska, A. Lenc, E. McKinley, B. Morgan, John Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. |
| author_sort | Galvin, T. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | We have acquired radio-continuum data between 70 MHz and 48 GHz for a sample of 19 southern starburst galaxies at moderate redshifts (0.067 < z < 0.227) with the aim of separating synchrotron and free–free emission components. Using a Bayesian framework, we find the radio continuum is rarely characterized well by a single power law, instead often exhibiting low-frequency turnovers below 500 MHz, steepening at mid to high frequencies, and a flattening at high frequencies where free–free emission begins to dominate over the synchrotron emission. These higher order curvature components may be attributed to free–free absorption across multiple regions of star formation with varying optical depths. The decomposed synchrotron and free–free emission components in our sample of galaxies form strong correlations with the total-infrared bolometric luminosities. Finally, we find that without accounting for free–free absorption with turnovers between 90 and 500 MHz the radio continuum at low frequency (ν < 200 MHz) could be overestimated by upwards of a factor of 12 if a simple power-law extrapolation is used from higher frequencies. The mean synchrotron spectral index of our sample is constrained to be α = −1.06, which is steeper than the canonical value of −0.8 for normal galaxies. We suggest this may be caused by an intrinsically steeper cosmic ray distribution. |
| first_indexed | 2025-11-14T10:30:17Z |
| format | Journal Article |
| id | curtin-20.500.11937-66555 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T10:30:17Z |
| publishDate | 2018 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-665552018-08-15T08:08:30Z The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum Galvin, T. Seymour, Nick Marvil, J. Filipovic, M. Tothill, N. McDermid, R. Hurley-Walker, Natasha Hancock, Paul Callingham, J. Cook, R. Norris, R. Bell, M. Dwarakanath, K. For, B. Gaensler, B. Hindson, L. Johnston-Hollitt, Melanie Kapinska, A. Lenc, E. McKinley, B. Morgan, John Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. We have acquired radio-continuum data between 70 MHz and 48 GHz for a sample of 19 southern starburst galaxies at moderate redshifts (0.067 < z < 0.227) with the aim of separating synchrotron and free–free emission components. Using a Bayesian framework, we find the radio continuum is rarely characterized well by a single power law, instead often exhibiting low-frequency turnovers below 500 MHz, steepening at mid to high frequencies, and a flattening at high frequencies where free–free emission begins to dominate over the synchrotron emission. These higher order curvature components may be attributed to free–free absorption across multiple regions of star formation with varying optical depths. The decomposed synchrotron and free–free emission components in our sample of galaxies form strong correlations with the total-infrared bolometric luminosities. Finally, we find that without accounting for free–free absorption with turnovers between 90 and 500 MHz the radio continuum at low frequency (ν < 200 MHz) could be overestimated by upwards of a factor of 12 if a simple power-law extrapolation is used from higher frequencies. The mean synchrotron spectral index of our sample is constrained to be α = −1.06, which is steeper than the canonical value of −0.8 for normal galaxies. We suggest this may be caused by an intrinsically steeper cosmic ray distribution. 2018 Journal Article http://hdl.handle.net/20.500.11937/66555 10.1093/mnras/stx2613 Oxford University Press fulltext |
| spellingShingle | Galvin, T. Seymour, Nick Marvil, J. Filipovic, M. Tothill, N. McDermid, R. Hurley-Walker, Natasha Hancock, Paul Callingham, J. Cook, R. Norris, R. Bell, M. Dwarakanath, K. For, B. Gaensler, B. Hindson, L. Johnston-Hollitt, Melanie Kapinska, A. Lenc, E. McKinley, B. Morgan, John Offringa, A. Procopio, P. Staveley-Smith, L. Wayth, Randall Wu, C. Zheng, Q. The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum |
| title | The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum |
| title_full | The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum |
| title_fullStr | The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum |
| title_full_unstemmed | The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum |
| title_short | The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum |
| title_sort | spectral energy distribution of powerful starburst galaxies - i. modelling the radio continuum |
| url | http://hdl.handle.net/20.500.11937/66555 |