The Prompt Inventory from Very Massive Stars and Elemental Abundances in Ly Alpha Systems

摘要

It has been proposed that very massive stars (VMSs) dominated heavy elementproduction until a metallicity threshold corresponding to [Fe/H]=-3 wasreached. This results in a prompt (P) inventory of elements, the abundances ofwhich were determined from observations of Galactic halo stars with [Fe/H]=-3.We calculate Omega_P(E) from the P inventory for a large number of elements inthe IGM. Using the available data on Omega(E_ion) for C IV, O VI, and Si IV inLy alpha systems, we find that the ionization fractions calculated fromOmega(E_ion)/Omega_P(E) are, within reasonable uncertainties, compatible withthe values estimated from ionization models for Ly alpha systems. Thisagreement appears to hold from z=0.09 to 4.6, indicating that the bulk of thebaryonic matter remains dispersed with a fixed chemical composition. Weconclude that the P inventory was established in the epoch prior to z=4.6. Thedispersal of processed baryonic matter to the general IGM is considered to bethe result of energetic VMS explosions that disrupted baryonic aggregates untilthe metallicity threshold was reached to permit normal astration. The formationof most galaxies is considered to have occurred subsequent to the achievementof this metallicity threshold in the IGM.