The evolving intergalactic medium - The uncollapsed baryon fraction in a cold dark matter universeThe time-varying density of the intergalactic medium (IGM) is calculated by coupling detailed numerical calculations of the thermal and ionization balance and radiative transfer in a uniform IGM of H and He to the linearized equations for the growth of density fluctuations in both gases and a dark component in a cold dark matter universe. The IGM density is identified with the collapsed baryon fraction. It is found that even if the IGM is never reheated, a significant fraction of the baryons remain uncollapsed at redshifts of four. If instead the collapsed fraction releases enough ionizing radiation or thermal energy to reionize the IGM by z greater than four as required by the Gunn-Peterson (GP) constraint, the uncollapsed fraction at z of four is even higher. The known quasar distribution is insufficient to supply the ionizing radiation necessary to satisfy the GP constraint in this case and, if stars are instead responsible, a substantial metallicity must have been produced by z of four.
Document ID
19930039639
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Shapiro, Paul R. (NASA Headquarters Washington, DC United States)
Giroux, Mark L. (Texas Univ. Austin, United States)
Babul, Arif (Cambridge Univ. Inst. of Astronomy, United Kingdom)
Date Acquired
August 16, 2013
Publication Date
January 1, 1991
Publication Information
Publication: In: After the first three minutes; Proceedings of the 1st Astrophysics Workshop, Univ. of Maryland, College Park, Oct. 15-17, 1990 (A93-23605 07-90)