The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum

Galvin, TJ; Seymour, N; Marvil, J; Filipović, MD; Tothill, NFH; McDermid, RM; Hurley-Walker, N; Hancock, PJ; Callingham, JR; Cook, RH; Norris, RP; Bell, ME; Dwarakanath, KS; For, B; Gaensler, BM; Hindson, L; Johnston-Hollitt, M; Kapińska, AD; Lenc, E; McKinley, B; Morgan, J; Offringa, AR; Procopio, P; Staveley-Smith, L; Wayth, RB; Wu, C; Zheng, Q

The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum

Galvin, TJ Seymour, N Marvil, J Filipović, MD Tothill, NFH McDermid, RM Hurley-Walker, N Hancock, PJ Callingham, JR Cook, RH Norris, RP Bell, ME

Dwarakanath, KS For, B Gaensler, BM Hindson, L Johnston-Hollitt, M Kapińska, AD Lenc, E McKinley, B Morgan, J Offringa, AR Procopio, P Staveley-Smith, L Wayth, RB Wu, C Zheng, Q

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Publication Type:: Journal Article
Citation:: Monthly Notices of the Royal Astronomical Society, 2018, 474 (1), pp. 779 - 799
Issue Date:: 2018-02-01

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Field	Value	Language
dc.contributor.author	Galvin, TJ	en_US
dc.contributor.author	Seymour, N	en_US
dc.contributor.author	Marvil, J	en_US
dc.contributor.author	Filipović, MD	en_US
dc.contributor.author	Tothill, NFH	en_US
dc.contributor.author	McDermid, RM	en_US
dc.contributor.author	Hurley-Walker, N	en_US
dc.contributor.author	Hancock, PJ	en_US
dc.contributor.author	Callingham, JR	en_US
dc.contributor.author	Cook, RH	en_US
dc.contributor.author	Norris, RP	en_US
dc.contributor.author	Bell, ME https://orcid.org/0000-0003-1767-5277	en_US
dc.contributor.author	Dwarakanath, KS	en_US
dc.contributor.author	For, B	en_US
dc.contributor.author	Gaensler, BM	en_US
dc.contributor.author	Hindson, L	en_US
dc.contributor.author	Johnston-Hollitt, M	en_US
dc.contributor.author	Kapińska, AD	en_US
dc.contributor.author	Lenc, E	en_US
dc.contributor.author	McKinley, B	en_US
dc.contributor.author	Morgan, J	en_US
dc.contributor.author	Offringa, AR	en_US
dc.contributor.author	Procopio, P	en_US
dc.contributor.author	Staveley-Smith, L	en_US
dc.contributor.author	Wayth, RB	en_US
dc.contributor.author	Wu, C	en_US
dc.contributor.author	Zheng, Q	en_US
dc.date.issued	2018-02-01	en_US
dc.identifier.citation	Monthly Notices of the Royal Astronomical Society, 2018, 474 (1), pp. 779 - 799	en_US
dc.identifier.issn	0035-8711	en_US
dc.identifier.uri	http://hdl.handle.net/10453/125932
dc.description.abstract	© 2018 The Author(s). We have acquired radio-continuum data between 70MHz 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 lowfrequency 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 500MHz the radio continuum at low frequency (v < 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.	en_US
dc.relation.ispartof	Monthly Notices of the Royal Astronomical Society	en_US
dc.relation.isbasedon	10.1093/mnras/stx2613	en_US
dc.subject.classification	Astronomy & Astrophysics	en_US
dc.title	The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum	en_US
dc.type	Journal Article
utslib.citation.volume	1	en_US
utslib.citation.volume	474	en_US
utslib.for	0201 Astronomical and Space Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
utslib.copyright.status	closed_access
pubs.issue	1	en_US
pubs.publication-status	Published	en_US
pubs.volume	474	en_US

Abstract:

© 2018 The Author(s). We have acquired radio-continuum data between 70MHz 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 lowfrequency 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 500MHz the radio continuum at low frequency (v < 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.

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http://hdl.handle.net/10453/125932