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Paper: The Impact of Cosmic Rays on Population III Star Formation
Volume: 393, New Horizons in Astronomy: Frank N. Bash Symposium 2007
Page: 275
Authors: Stacy, A.; Bromm, V.
Abstract: We explore the implications of a possible cosmic ray (CR) background generated during the first supernova explosions that end the brief lives of massive Population III stars. We show that such a CR background could have significantly influenced the cooling and collapse of primordial gas clouds in minihalos around redshifts of z ∼ 15−20, provided the CR flux was sufficient to yield an ionization rate greater than about 10−19 s−1 near the center of the minihalo. The presence of CRs with energies less than approximately 107 eV would indirectly enhance the molecular cooling in these regions, and we estimate that the resulting lower temperatures in these minihalos would yield a characteristic stellar mass as low as ∼ 10MSolar. CRs have a less pronounced effect on the cooling and collapse of primordial gas clouds inside more massive dark matter halos with virial masses greater than approximately 108MSolar at the later stages of cosmological structure formation around z ∼ 10 − 15. In these clouds, even without the CR flux, the molecular abundance is already sufficient for cooling to the floor set by the temperature of the cosmic microwave background.
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