A model of metallicity evolution in the early universe

G. J. Wasserburg, Y. Z. Qian

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18 Scopus citations


We apply the phenomenological model used to explain the abundances of Fe and r-process elements in very metal-poor stars in the Galaxy to [Fe/H] of damped Lyα systems. It is assumed that the first stars that formed after the big bang were very massive and that they promptly enriched the interstellar medium to [Fe/H] ∼ -3, at which metallicity the formation of normal stars took over. Subsequent Fe enrichment was provided by Type II supernovae. The range of [Fe/H] at a given redshift z for damped Lyα systems is explained by the time t(Black star) after the big bang at which normal star formation started in an individual protogalactic system. The average t(Black star) is ≈80% the age of the universe for damped Lyα systems at z ≈ 1.5-4.5, indicating a long delay between the big bang and the turn-on of protogalaxies. It is inferred that a substantial fraction of the total baryonic matter may not have been aggregated into protogalaxies with normal star formation events until a late time corresponding to z ∼ 1.5. The data near z = 2.2 indicate that the rate of turn-on of protogalaxies was initially very low and that it slowly reached a maximum at ∼3 Gyr after the big bang. This rate of turn-on of galaxies may be important in understanding the rate of formation of quasars.

Original languageEnglish (US)
Pages (from-to)L99-L102
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - Aug 1 2000

Bibliographical note

Funding Information:
We want to thank Roger Blandford and Marc Kamionkowski for their ongoing interest in this work and for generously giving their time and providing, as usual, deep cosmic insights and education. Maarten Schmidt has been kind enough to expose us to the details of quasar distribution. This work was supported in part by the Department of Energy under grant DE-FG02-87ER40328 to Y.-Z. Q. and by NASA under grant NAG5-4083 to G. J. W., Caltech Division Contribution 8728(1059).


  • Galaxies: abundances
  • Galaxies: evolution
  • Quasars: absorption lines


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