2003ApJ...589...53H

A prediction of standard inflationary cosmology is that the elemental composition of the medium out of which the earliest stars and galaxies condensed consisted primarily of hydrogen and helium ⁴He, with small admixtures of deuterium, lithium ⁷Li, and ³He. The most redshifted quasars, galaxies, and Lyα absorbers currently observed, however, all exhibit at least some admixture of heavier elements, as do the most ancient stars in the Galaxy. Here we examine ways in which the abundance of these same elements, if present before the epoch of Population III formation, might be observationally established or ruled out.