Mathematics – Logic
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009phdt........30m&link_type=abstract
PhD thesis, Ludwig Maximilian University, 229 pages, 2009
Mathematics
Logic
5
Cosmology: Theory, Early Cosmic Structures
Scientific paper
Gas cooling and star formation (SF) is still an unsolved problem in astrophysics. We investigate its redshift/time evolution and compare different modeling running high-resolution, three-dimensional, N-body/hydrodynamical simulations, including non-equilibrium, atomic and molecular chemistry, SF prescriptions, metal pollution, and feedback effects. We also study how the primordial SF changes accordingly to different semi-analytical approaches, cosmological parameters, initial set-ups and critical metallicity for the transition from a metal-free regime to a standard, enriched one. The H_2 molecule is confirmed to be the most relevant coolant in early times; inclusion of HD cooling results in a ˜ 10%-20% higher gas clumping; metal cooling at low temperatures can have a significant impact on the formation and evolution of first objects; typical numerical ``sub-grid'' models fail in following the cooling of primordial gas; metal-free SF regime is negligible with respect to the global SF rate, because of the very short first star life-times; primordial pollution up to ˜ 10^{-3} Z_&sun;, or higher, is extremely rapid and allows for a very fast transition to standard SF regimes; the different SF rates and metal enrichment got for different critical metallicities are distinguishable and span about one order of magnitude. Given the importance of the initial stellar mass distribution function, an analytical model describing its possible derivation from turbulent dissipation is presented.
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