[astro-ph/0507439] Heavy Element Production in Inhomogeneous Big Bang Nucleosynthesis

Authors:  S. Matsuura, S. Fujimoto, S. Nishimura, M. Hashimoto, K. Sato
Abstract:  We present a new astrophysical site of the big bang nucleosynthesis (BBN) that are very peculiar compared with the standard BBN. Some models of the baryogenesis suggest that very high baryon density regions were formed in the early universe. On the other hand, recent observations suggest that heavy elements already exist in high red-shifts and the origin of these elements become a big puzzle. Motivated by these, we investigate big bang nucleosynthesis in very high baryon density regions. Big bang nucleosynthesis proceeds in proton rich environment and it is known to be p-process like. However, by taking very heavy nuclei into account, we find that big bang nucleosynthesis proceeds both p-process and r-process simultaneously. P-nuclei such as $^{92}$Mo, $^{94}$Mo, $^{96}$Ru, $^{98}$Ru are also synthesized.
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Garth Antony Barber
Posts: 59
Joined: July 19 2005
Affiliation: Published independent

[astro-ph/0507439] Heavy Element Production in Inhomogeneous

Post by Garth Antony Barber » July 22 2005

Is there a problem with the standard model? The paper seems to suggest there is and proposes an inhomogeneous BBN to explain the existence of early metallicity:
It has become clear that the evolution of matter started earlier than we have known before. For example, Wilkinson Microwave Anisotropy Probe (WMAP) data suggests that reionization began when z ~20 [C.L. Bennet, et al., Astrophys. J. Suppl. 148, 1, (2003)]. According to Refs. [astro-ph/0308005] [M. Dietrich, I. Appenzeller, M. Vestergaard, and S.J. Wagner, Astrophys. J. 564, 581 (2002)], star formation activity started when z >= 10. In addition, it is known that the quasar metallicity did not significantly change from the time of high redshift to the present time [astro-ph/0307557]. Recently a galaxy at z=10.0 was observed [astro-ph/0403025].Other evidences of heavy elements from the high redshifts are in [astro-ph/0309646][astro-ph/0405286][astro-ph/0110123][astro-ph/0201417][astro-ph/0303424] [astro-ph/0305413]
From the last papers:
There thus appears to be no evolution of QSO metallicity to z~6. Our results suggest that massive, chemically enriched galaxies formed within 1 Gyr of the Big Bang. If this chemical enrichment was produced by Type Ia supernovae, then the progenitor stars formed at z ~ 20 +/- 10, in agreement with recent estimates based on the cosmic microwave background. These results also support models of an evolutionary link between star formation, the growth of supermassive black holes and nuclear activity.
This somewhat surprising conclusion may be an indication that the intergalactic medium was enriched in metals at redshifts much greater than 5, perhaps by the sources responsible for its reionization
Is there a problem explaining this early metallicity?
The standard answer is to say "PopIII stars", but during which epochs and with what mass range? With the constraints on the mass function of such a population can the ubiquitous nature of reionisation and early metallciity be so explained?

Garth Antony Barber
Posts: 59
Joined: July 19 2005
Affiliation: Published independent

[astro-ph/0507439] Heavy Element Production in Inhomogeneous

Post by Garth Antony Barber » July 28 2005

Is there a problem explaining this early metallicity?
The standard answer is to say "PopIII stars", but during which epochs and with what mass range? With the constraints on the mass function of such a population can the ubiquitous nature of reionisation and early metallciity be so explained?
This recent paper by Ohkubo, Umeda, Maeda, Nomoto, Tsuruta and Rees astro-ph/0507593 may give the answer.
We calculate evolution, collapse, explosion, and nucleosynthesis of Population III very-massive stars with 500M⊙ and 1000M⊙. Presupernova evolution is calculated in spherical symmetry. Collapse and explosion are calculated by a two-dimensional code, based on the bipolar jet models. We compare the results of nucleosynthesis with the abundance patterns of intracluster matter, hot gases in M82, and extremely metal-poor stars in the Galactic halo.
It was found that both 500M⊙ and 1000M⊙ models enter the region of pair instability but continue to undergo core collapse. In the presupernova stage, silicon burning regions occupy a large fraction, more than 20% of the total mass. For moderately aspherical explosions, the patterns of nucleosynthesis match the observational data of both intracluster medium and M82. Our results suggest that explosions of Population III core-collapse very-massive stars contribute significantly to the chemical evolution of gases in clusters of galaxies. For Galactic halo stars, our [O/Fe] ratios are smaller than the observational abundances. However, our proposed scenario is naturally consistent with this outcome. The final black hole masses are about 500M⊙ for our most massive (1000M⊙) models. This result may support the view that Population III very massive stars are responsible for the origin of intermediate mass black holes which were recently reported to be discovered.
My question is:"How many PopIII stars are needed to account for the observed re-ionisation and early metallicity - and is this number consistent with Omega_{baryon}?"

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