An Empirically-Calibrated Model For Interpreting the Evolution of Galaxies During the Reionization Era

[Abridged] We develop a simple star formation model whose goal is to interpret the emerging body of observational data on star-forming galaxies at z>~6. The efficiency and duty cycle of the star formation activity within dark matter halos are determined by fitting the luminosity functions of Lya emitter and Lyman-break galaxies at redshifts z~5-6. Using our model parameters we predict the likely abundance of star forming galaxies at earlier epochs and compare these to the emerging data in the redshift interval 7<z<10. We find that the abundance of luminous Lyman-break galaxies in the 500 Myr between z~6 and 10 can be naturally explained by the hierarchical assembly of dark matter haloes; there is only marginal evidence for strong physical evolution. In contrast, the first estimates of the abundance of less luminous star forming galaxies at z=9-10 are higher than predicted and, if verified by further data, may suggest a top-heavy stellar mass function at these early epochs. Although these abundances remain uncertain because of the difficulty of spectroscopic confirmation and cosmic variance, even a modest improvement in survey capability with present or upcoming facilities should yield great progress. In this context, we use our model to consider those observational techniques that hold the most promise and make predictions for specific surveys that are, or will soon be, underway. We conclude that narrowband Lya emitter surveys should be efficient on searches at z~7-8; however, such conventional surveys are unlikely to detect sufficient galaxies at z~10 to provide useful constraints. For this reason, gravitational lensing offers the best prospect for probing the z~10 universe prior to JWST.