Lyman Break Galaxies and Reionization of Universe

We present the star formation histories, luminosities, colors, mass to lightratios, and halo masses of "galaxies" formed in a simulation of cosmologicalreionization. We compare these galaxies with Lyman Break Galaxies observed athigh redshift. While the simulation is severely limited by the small box size,the simulated galaxies do appear as fainter cousins of the observed ones. Theyhave similar colors, and both simulated and observed galaxies can be fittedwith the same luminosity function. This is significant to the process ofreionization since in the simulation the stars alone are responsible forreionization at a redshift consistent with that of the Gunn-Peterson troughseen in the absorption spectra of QSO's. The brightest galaxies at z = 4 areindeed quite young in accord with observational studies. But these brightestgalaxies are free riders - they contributed only about 25% to the reionizationof the universe at z > 6. Instead, the bulk of the work was done by dimmergalaxies, those that fall within the 28 < I < 30 magnitude range at z = 4.These dimmer galaxies are not necessarily less massive than the brightest ones.Comment: submitted to Ap