The radio continuum emission of star forming galaxies at low to high redshift

In this thesis, the radio-continuum emission of starburst galaxies is explored to understand the physical processes that trace star formation. Separating and constraining these processes require a broad, densely sampled spectral energy distribution that can be used to apply and constrain various radiative transfer models. Existing tracers of star formation include a suite of multi-wavelength diagnostics, including UV, optical, infrared, nebular transitions, and radio continuum. At present, optical and near infrared observations have been the most successful at probing the high redshift volume and constraining the star formation at the earliest epochs of the Universe. However, such approaches are critically awed in that they are subject to the effects of dust obscuration, requiring sophisticated methods to recover the intrinsic luminosities of the optical tracers of star formation. In the high redshift Universe, these corrections are increasingly compromised and uncertain. Radio-continuum measurements of star formation have the potential to be the most reliable in this high redshift regime because they are not affected by the presence of dust, allowing observers to acquire uncompromised measures of star formation. At frequencies below _ 2 GHz, the radio continuum is made up overwhelmingly by non-thermal synchrotron emission, produced by near light speed cosmic rays interacting with the large-scale magnetic structure of a galaxy. Although this type of emission is not a direct product of stars, it has been reasonably well calibrated to exploit the far-infrared to radio correlation to obtain a measure of star formation. Our current understanding of the far-infrared to radio correlation suggests that there should be an evolution as a function of redshifts; however, observationally evidence both confirms and rejects this evolution hypothesis. As the far-infrared to radio correlation is the foundation of star formation rate indicators based on the radio continuum for frequencies where synchrotron emission is a significant component of the observed spectrum, there is a requirement to investigate, and if necessary repair, radio-based star formation rate measures in preparation for radio telescopes like the Square Kilometre Array. Throughout my candidature, I have studied the spectral energy distribution of 30 local galaxies that were selected based on their high star formation rates, as indicated by their radio and infrared emission data collected from existing surveys. Across a broad frequency range spanning 80MHz to 50 GHz, the underlying physical processes driving the radio continuum have been disentangled. By comparing these products to other multi-wavelength indicators of star formation, we can begin to understand the radio-based tracers for faint star forming galaxies at high redshift that the next generation of radio telescopes will reveal