{
  "id": "1710.01967",
  "version": "v1",
  "published": "2017-10-05T11:15:49.000Z",
  "updated": "2017-10-05T11:15:49.000Z",
  "title": "The Spectral Energy Distribution of Powerful Starburst Galaxies I: Modelling the Radio Continuum",
  "authors": [
    "T J Galvin",
    "N Seymour",
    "J Marvil",
    "M D Filipovic",
    "N F H Tothill",
    "R M McDermid",
    "N Hurley-Walker",
    "P J Hancock",
    "J R Callingham",
    "R H Cook",
    "R P Norris",
    "M E Bell",
    "K S Dwarakanath",
    "B For",
    "B M Gaensler",
    "L Hindson",
    "M Johnston-Hollitt",
    "A D Kapińska",
    "E Lenc",
    "B McKinley",
    "J Morgan",
    "A R Offringa",
    "P Procopio",
    "L Staveley-Smith",
    "R B Wayth",
    "C Wu",
    "Q Zheng"
  ],
  "categories": [
    "astro-ph.GA"
  ],
  "abstract": "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 characterised 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 to 500\\,MHz the radio-continuum at low frequency ($\\nu < 200$\\,MHz) could be overestimated by upwards of a factor of twelve if a simple power law extrapolation is used from higher frequencies. The mean synchrotron spectral index of our sample is constrained to be $\\alpha=-1.06$, which is steeper then the canonical value of $-0.8$ for normal galaxies. We suggest this may be caused by an intrinsically steeper cosmic ray distribution.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2017-10-05T11:15:49.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "spectral energy distribution",
      "radio continuum",
      "powerful starburst galaxies",
      "steeper cosmic ray distribution",
      "free-free emission components"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 0,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}