Verschuur said:
Lastly, if a source of electrons can be identified and a mechanism for clustering suggested, is it still possible to account for production of the high-frequency continuum radiation through invoking free-free emission from electrons?

I assume that Verschuur is talking about black-body radiation here. Free-free (i.e., Bremsstrahlung) radiation can theoretically produce BB radiation, but it will be vastly overshadowed by spectral lines from free-bound emissions. Only graphite and supercritical hydrogen have been demonstrated to produce BB radiation in the laboratory. In space, I'm going with supercritical hydrogen.