A Lyman Continuum Explorer - LyContEx

Abstract

GALEX has identified large numbers of extra galactic objects that are too faint to be observed by FUSE. These star forming systems are potential sources of Lyman continuum (Lyc) radiation and may contribute to the metagalactic background radiation that ionizes most of the baryons in the universe. By measuring the level of Lyc radiation leaking from these galaxies we can quantify the contribution of stars, relative to quasars, to the ionizing background at low redshift (0.025 <~ z <~ 0.4) and provide insight into the reionization processes at high redshift. A meter class instrument with a moderate spectral dispersion, wide-field, multi-object spectrograph can detect Lyc leak from a statistically significant number of these galaxies, if the average escape fraction f_{esc} <~ 1%. Such an instrument will have enormous discovery potential because of the large number of extra-galactic objects that exist within its grasp. LyContEx will be scientifically productive, synergistic with existing surveys, and can be developed into a far ultraviolet mission in the near future.