FIRSTLIGHT: Cosmological simulations of first galaxies at cosmic dawn

Using the FirstLight database of 300 zoom-in cosmological simulations we provide rest-frame UV-optical spectral energy distributions of galaxies with complex star-formation histories that are coupled to the non-uniform gas accretion history of galactic halos during cosmic dawn. The population at any redshift is very diverse ranging from starbursts to quiescent galaxies even at a fixed stellar mass. The FirstLight simulations make predictions on the rest-frame UV-optical absolute magnitudes, colors and optical emission lines of galaxies at z = 6-12 that will be observed for the first time with JWST and the next generation of telescopes in the coming decade.