Massive black holes and light-element nucleosynthesis in a baryonic universe

Details Massive black holes and light-element nucleosynthesis in a baryonic universe Massive black holes and light-element nucleosynthesis in a baryonic universe

Jan 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...438...40g&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 438, no. 1, p. 40-48

Astronomy and Astrophysics

Astronomy

23

Astronomical Models, Baryons, Black Holes (Astronomy), Light Elements, Nuclear Fusion, Universe, Abundance, Cosmology, Dark Matter, Normal Density Functions

Scientific paper

We reexamine the model proposed by Gnedin & Ostriker (1992) in which Jeans mass black holes (MBH approximately = 106 solar mass) form shortly after decoupling. There is no nonbaryonic dark matter in this model, but we examine the possibility that Omegab is considerably larger than given by normal nucleosynthesis. Here we allow for the fact that much of the high baryon-to-photon ratio material will collapse leaving the universe of remaining material with light-element abundances more in accord with the residual baryonic density (approximately = 10-2) than with Omega0 and the initial baryonic density (approximately = 10-1). We find that no reasonable model can be made with random-phase density fluctuations, if the power on scales smaller than 106 solar mass is as large as expected. However, phase-correlated models of the type that might occur in connection with topological singularities can be made with Omegab h2 = 0.013 +/- 0.001, 0.15 approximately less than Omega0 approximately less than 0.4, which are either flat (Omegalambda = 1 - Omega0) or open (Omegalambda = 0) and which satisfy all the observational constraints which we apply, including the large baryon-to-total mass ratio found in the X-ray clusters. The remnant baryon density is thus close to that obtained in the standard picture (Omegab h2 = 0.0125 +/- 0.0025; Walker et al. 1991). The spectral index implied for fluctuations in the baryonic isocurvature scenario, -1 less than m less than 0, is in the range expected by other arguments based on large-scale structure and microwave fluctuation constraints. The dark matter in this picture is in the form of massive black holes. Accretion onto them at early epochs releases high-energy photons which significantly heat and reionize the universe. But photodissociation does not materially change light-element abundances. A typical model gives bar-y approximately = 1 x 10-5, ne/nH(z = 30) approximately = 0.1, and a diffuse gamma-ray background at 100 keV near the Cosmic Background Explorer Satellite (COBE) limit of the order of 10% of that observed which originates from high-redshift quasars. Reionization in this model occurs at redshift 600 and reaches (H II/Htot approximately = 0.1-0.2.

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