High-Redshift Supernovae and the Metal-Poor Halo Stars: Signatures of the First Generation of Galaxies

Recent evidence on the metal content of the high-redshift Lyman alpha forestseen in quasar spectra suggests that an early generation of galaxies enrichedthe intergalactic medium (IGM) at z ~ 5. We calculate the number of supernovaethat need to have taken place to produce the observed metallicity. Theprogenitor stars of the supernovae should have emitted $\sim 20$ ionizingphotons for each baryon in the universe, i.e., more than enough to ionize theIGM. We calculate that the rate of these supernovae is such that about one ofthem should be observable at any time per square arc minute. Their fluxes are,of course, extremely faint: at z=5, the peak magnitude should be K=27 with aduration of ~ 1 year. However, these supernovae should still be the brightestobjects in the universe beyond some redshift, because the earliest galaxiesshould form before quasars and they should have very low mass, so theirluminosities should be much lower than that of a supernova. We also show that, under the assumption of a standard initial mass function,a significant fraction of the stars in the Galactic halo should have formed inthe early galaxies that reionized and enriched the IGM, and which later musthave merged with our Galaxy. These stars should have a more extended radialdistribution than the observed halo stars.Comment: To be published in ApJ Letter