SUPERNOVAE AND THE SPECTRA OF HIGH-REDSHIFT GALAXIES

We estimate the effect of supernova remnants (SNR) on the UV continuum of galaxies. We show that the radiation from the remnants may lead to a very small rest frame Lyman break. We calculate the appearance of such galaxies at high redshift, and conclude that even galaxies with negligible rest frame Lyman break will have large observed breaks because of absorption by intervening Lya clouds. Star-forming galaxies at high redshifts may thus supply the ionizing radiation background without this radiation being observable in the spectrum. Emission from SNR also leads to a much harder galactic spectrum, especially shortward of 228 angstrom. This means that high-ionization lines observed in high-redshift radio galaxies or metal line systems may result from photo-ionization by hard radiation emerging from hot SNR.