INTERPRETING THE GLOBAL 21-cm SIGNAL FROM HIGH REDSHIFTS. II. PARAMETER ESTIMATION FOR MODELS OF GALAXY FORMATION

Following our previous work, which related generic features in the sky-averaged (global) 21-cm signal to properties of the intergalactic medium, we now investigate the prospects for constraining a simple galaxy formation model with current and near-future experiments. Markov-Chain Monte Carlo fits to our synthetic data set, which includes a realistic galactic foreground, a plausible model for the signal, and noise consistent with 100 hr of integration by an ideal instrument, suggest that a simple four-parameter model that links the production rate of Ly alpha, Lyman-continuum, and X-ray photons to the growth rate of dark matter halos can be well-constrained (to similar to 0.1 dex in each dimension) so long as all three spectral features expected to occur between 40 less than or similar to nu/MHz less than or similar to 120 are detected. Several important conclusions follow naturally from this basic numerical result, namely that measurements of the global 21-cm signal can in principle (i) identify the characteristic halo mass threshold for star formation at all redshifts z greater than or similar to 15, (ii) extend z less than or similar to 4 upper limits on the normalization of the X-ray luminosity star formation rate (L-X-SFR) relation out to z similar to 20, and (iii) provide joint constraints on stellar spectra and the escape fraction of ionizing radiation at z similar to 12. Though our approach is general, the importance of a broadband measurement renders our findings most relevant to the proposed Dark Ages Radio Explorer, which will have a clean view of the global 21-cm signal from similar to 40 to 120 MHz from its vantage point above the radio-quiet, ionosphere-free lunar far-side.