The Cosmic Star Formation Rate from the Faintest Galaxies in the Unobservable Universe

Understand

Observations of high-z galaxies and gamma-ray bursts now allow for empirical studies during reionization.

• However, even deep surveys see only the brightest galaxies at any epoch and must extrapolate to arbitrary lower limits to estimate the total rate of star formation.
• We first argue that the galaxy populations seen in LBG surveys yield a GRB rate at z > 8 that is an order of magnitude lower than observed.
• We find that integrating the inferred UV luminosity functions down to M_UV ~ -10 brings LBG- and GRB-inferred SFR density values into agreement up to z ~ 8.