Primordial Molecular Emission in Population III Galaxies

We study formation of molecules in primordial prestellar clumps and evaluatethe line luminosities to assess detectability by next-generation facilities. Ifthe initial H_2 fraction is sufficiently high, HD becomes an important coolantin the clumps. The luminosity from such HD cooling clumps is lower than thatfrom H_2 cooling ones because of lower temperature (<100K). As for Lireactions, we include the three-body LiH formation approximately. The Limolecular fraction remains very low (<10^{-3}) throughout the evolution owingto the high dissociative reaction rate of LiH +H -> Li + H_2. LiH does notbecome an important coolant in any density range. The luminous emission linesfrom the prestellar cores include H_2 rovibrational lines: 1-0 Q(1), 1-0 O(3),1-0 O(5), and pure rotational lines: 0-0 S(3), 0-0 S(4), 0-0 S(5). Thenext-generation facilities SPICA and JWST are able to detect H_2 emission in alarge pre-galactic cloud that forms metal-free stars at a high rate of \sim10^3 M_s/yr at redshift z<10. We also derive an analytical expression for theluminosity that reproduces the numerical results.Comment: 32 pages, 13 figures, 3 tables, accepted PAS