by Joe Callingham (ASTRON)

Abstract: One of the most common assumptions in radio astronomy is that the continuum spectrum of a radio source follows a simple power-law. Such an assumption is being challenged by the data being produced by the new sophisticated megahertz-sensitive telescopes and broadband gigahertz-receivers, as we can now sample the spectra of radio sources at a level of detail never before achievable. We are finding that a power-law description is inappropriate for many radio sources, particularly at low frequencies where absorption processes become significant. I will outline in my talk how low-frequency absorption processes provides us with a unique tool to test radio galaxy evolutionary models, mass loss scenarios of progenitor stars to supernovae, particle acceleration processes in pulsar wind nebulae, and a way to identify high-redshift galaxies. In particular, I will demonstrate that probing these absorption processes opens up an untapped discovery space for exotic objects that have been missed in more traditional spectral searches.