2002/03/13 by Yong-Zhong Qian, Y. -Z. Qian, W. L. W. Sargent +1 · 2 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/340641
published as Astrophys.J. 569 (2002) L61-L64 · 11 pages, to appear in ApJL
arxiv created 2002/03/13 · openalex publication_date 2002/04/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/04
It has been proposed that very massive stars (VMSs) dominated heavy-element production until a "metallicity" threshold corresponding to [Fe/H] ≈ -3 was reached. This results in a prompt ( P ) inventory of elements, the abundances of which were determined from observations of Galactic halo stars with [Fe/H] ≈ -3. We calculate Ω P (E) from the P inventory for a large number of elements in the intergalactic medium (IGM). Using the available data on Ω(E ion ) for C IV, O VI, and Si IV in Lyα systems, we find that the ionization fractions calculated from Ω(E ion )/Ω P (E) are, within reasonable uncertainties, compatible with the values estimated from ionization models for Lyα systems. This agreement appears to hold from z ~ 0.09 to ~4.6, indicating that the bulk of the baryonic matter remains dispersed with a fixed chemical composition. We conclude that the P inventory was established in the epoch prior to z ~ 4.6. The dispersal of processed baryonic matter to the general IGM is considered to be the result of energetic VMS explosions that disrupted baryonic aggregates until the "metallicity" threshold was reached to permit normal astration. The formation of most galaxies is considered to have occurred subsequent to the achievement of this metallicity threshold in the IGM.