THE EDDINGTON LIMIT IN COSMIC RAYS: AN EXPLANATION FOR THE OBSERVED FAINTNESS OF STARBURSTING GALAXIES

We show that the luminosity of a star-forming galaxy is capped by the production and subsequent expulsion of cosmic rays from its interstellar medium. By defining an Eddington luminosity in cosmic rays, we show that the star formation rate of a given galaxy is limited by its mass content and the cosmic-ray mean free path. When the cosmic-ray luminosity and pressure reach a critical value as a result of vigorous star formation, hydrostatic balance is lost, a galactic-scale cosmic-ray-driven wind develops, and star formation is choked off. Cosmic-ray pressure driven winds are likely to produce wind velocities in proportion to and significantly in excess of the galactic escape velocity. It is possible that cosmic-ray feedback results in the Faber-Jackson relation for a plausible set of input parameters that describe cosmic-ray production and transport, which are calibrated by observations of the Milky Way's interstellar cosmic rays as well as other nearby galaxies.