Speaker
Description
Observations with the James Webb Space Telescope (JWST) have revealed a higher than expected ultraviolet (UV) luminosity density as well as the presence of luminous, massive galaxies already a few hundred million years after the Big Bang. The physical origin of these observational findings is not well understood but possibly related to an increased star formation efficiency at early cosmic times. In this talk, I will introduce FIREbox-HR, a new cosmological hydrodynamical simulation from the Feedback in Realistic Environments (FIRE) project, that offers insights into the star formation efficiency of galaxies during the first billion years of cosmic time. FIREbox-HR resimulates the cosmic volume of the original FIREbox run with eight times higher mass resolution down to 𝑧 ~ 6 enabling it to robustly model the abundance of galaxies across a broad range in luminosity (down to M_UV ~ -12), stellar mass, and halo mass during the Epoch of Reionization and late Cosmic Dawn (z ~ 6-15). In contrast to previous theoretical works, the UV luminosity functions and the cosmic UV luminosity density predicted by FIREbox-HR are in excellent agreement with observations out to the highest observed redshifts. Subsequently, I will discuss the implications of this finding for the star formation efficiencies of galaxies during the Epoch of Re-ionization and inferences that can be drawn for even earlier cosmic times. Future observations of UV faint galaxies at z > 12 will provide an opportunity to further test these predictions and deepen our understanding of star formation during Cosmic Dawn.
