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J. H. Wise, T. Abel (Penn State University)
We explore the consequences of radiative feedback on early generations of star formation. Growing evidence from recent simulations requires that the first generation to be mainly composed of massive stars. Cooling via molecular hydrogen is the main mechanism that allows the formation of these stars. However, copious amounts of UV photons, which effectively dissociate H2, are produced by these massive stars. A reduced number fraction of molecular hydrogen inhibits cooling within the halos, thus increases the required halo mass to form a luminous object. By using results from Eulerian adaptive mesh refinement cosmological hydrodynamics simulations, we construct a semi-analytic method to trace the minimum mass of a dark matter halo required to form stars as a function of redshift. With this minimum mass in hand, the extended Press-Schechter formalism allows us to calculate the density of these halos; therefore, we can follow the densities of these halos and predict Pop III SNe rates throughout redshift space. SNe rates per sky area of events are presented. We also show the evolution of metallicity due to Pop III objects by using these rates and metal yields from metal-free stellar models. The metals expelled by Pop III SNe curiously coincide with the metallicities ([M/H]\odot = -4) of metal-poor stars, which hints at a relation between the first generation of stars and these metal-poor stars. Furthermore, we can estimate the brightness of these SNe via the nickel yields, which allows us to compute expected number counts for observations with SIRTF, NGST, and PRIME. The uncertainties of the typical initial Pop III stellar masses and their stellar evolution models translate to uncertainties in their expected supernovae rates. Nevertheless, numbers as large as 1.3 SNe per square arcminute per year seem plausible.
The author(s) of this abstract have provided an email address for comments about the abstract: jwise@astro.psu.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.