paper

The Spectral Energy Distribution of Powerful Starburst Galaxies I: Modelling the Radio Continuum

arXiv:1710.01967 · doi:10.1093/mnras/stx2613

Abstract

We have acquired radio continuum data between 70\,MHz and 48\,GHz for a sample of 19 southern starburst galaxies at moderate redshifts () 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 (\,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 , which is steeper then the canonical value of for normal galaxies. We suggest this may be caused by an intrinsically steeper cosmic ray distribution.

References in corpus (8)

Cited by in corpus (26)