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B. W. O'Shea (UCSD/UIUC), M. L. Norman (UCSD)
We use numerical simulations to study the effects of radiative feedback from the first generation of stars. These stars are believed to be very massive (in the range of 30-300 solar masses) and copious emitters of ultraviolet light. In addition, it is possible that these massive primordial stars end their lives in pair instability supernovae, which can be up to 100 times more energetic than standard Type II supernovae and convert approximately half of the initial stellar mass into metals.
The numerical calculations are done using the publicly-available adaptive mesh refinement cosmology code Enzo (http://cosmos.ucsd.edu/enzo). We perform the simulations in a box which is 0.3 Mpc/h on a side and scaled such that the evolution of the first generation of stars can be followed from the formation of the initial dark matter halo to the formation of the first protostellar object at z = 17.8.
We then insert a HII region by hand. This is done using a combination of the 3D ray-tracing scheme by Abel & Sokasian to determine the full extent of the HII region and one-dimensional radiation hydrodynamical calculations by Whalen et al. to correctly capture the behavior of gas within the virial radius of the Pop III halo. Several halos in the immediate vicinity are completely ionized by the end of the star's main sequence lifetime.
The HII region causes significant positive feedback on nearby halos due to freeing of electrons in these halos from ionizing radiation during the main sequence lifetime of the star. This causes the molecular hydrogen fraction to increase by almost an order of magnitude when compared to the same halos in a simulation which has not been ionized, and can spur the formation of the second generation of stars.
The author(s) of this abstract have provided an email address for comments about the abstract: bwoshea@cosmos.ucsd.edu
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.