Metal enrichment of the intergalactic medium and production of massive black holes

Y. Z. Qian, G. J. Wasserburg

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3 Scopus citations

Abstract

A model for the chemical evolution of the intergalactic medium (IGM) is presented using theoretical yields of very massive stars (VMSs; MVMS > 100 M) and Type II supernovae (SNe II). It is shown that if [Si/C] is indeed as high as ∼0.7 in the IGM, then VMSs (MVMS ≈ 140-260 M) associated with pair-instability supernovae (PI-SNe) in low-mass (∼ 105 M) halos at high redshift must produce at least 50% of the Si. The remainder is from later galactic outflows of SN II debris, which also provide most of the C and O. Both sources are required to account for the metal inventory in the IGM. The early VMS production must continue until redshift z ∼ 15 so that the efficiency of VMS formation per low-mass halo is significantly below unity. Contributions from the later galactic outflows mainly occur at z ∼ 4-6. Using a Salpeter initial mass function, we infer that the number of VVMS ≈ 260-2000 M) producing massive black holes (MBHs) with an average mass (MMBH) ∼ 270-550 M is ≈0.72 times the number of VMSs associated with PI-SNe. The amount of metals (particularly Si) in the IGM that is attributable to PI-SNe is thus closely coupled with the total mass of MBHs produced in epochs prior to galaxy formation. Production of ∼50% of the Si in the IGM by PI-SNe corresponds to an early inventory of MBHs that constitutes a fraction ∼(4-8) × 10-5 of the total baryonic mass in the universe. This is comparable to the global mass budget of the central supermassive black holes (SMBHs) in present-day galaxies. The corresponding occurrence rates in each halo of ∼ 105 Modot; during the epoch of VMS formation at z ≳ 15 are ∼0.9 Gyr-1 for VMSs associated with PI-SNe and ∼0.6 Gyr-1 for the concomitant more massive stars producing MBHs. These rates may be of use to studies of H2 dissociation and reionization and to models of SMBH formation.

Original languageEnglish (US)
Pages (from-to)845-852
Number of pages8
JournalAstrophysical Journal
Volume635
Issue number2 I
DOIs
StatePublished - Dec 20 2005

Keywords

  • Galaxies: formation
  • Intergalactic medium
  • Nuclear reactions, nucleosynthesis, abundances

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