Detecting the Transition From Pop III to Pop II Stars

We discuss the cosmological significance of the transition from the Pop III to Pop II mode of star formation in the early universe, and when and how it may occur in primordial galaxies. Observations that could detect this transition include those of element abundances in metal-poor Galactic halo stars, and of the helium reionization and associated heating of the intergalactic medium. We suggest that gamma-ray bursts may be a better probe of the end of the first-stars epoch than of Pop III stars.