AAS 197, January 2001
Session 72. Cosmology from z=1100 to 1
Display, Wednesday, January 10, 2001, 9:30am-7:00pm, Exhibit Hall

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[72.08] Photoionization of Primordial Halos by the First Stars

D. Whalen, M. L. Norman, A. Razoumov (UCSD), T. Abel (CFA)

Recent advances in numerical cosmology reveal that the first luminous objects in the universe were likely solitary massive (10-50 M\odot) stars shrouded by primordial molecular hydrogen and helium envelopes with zero metallicity. These young stars ignited with intense UV fluxes and fast stellar winds that photoionized, photodissociated and swept up their parent clouds. Radiative transfer and hydrodynamics govern how photons filtered out of the cloud and contributed to the UV environment of the early universe. These processes also dictate the timescales over which the first stars dispersed their birth clouds, setting limits on the rate of subsequent star formation.

We present a numerical method for computing the transport of ionizing and dissociating radiation in primordial stellar halos. The equation of radiative transfer is solved along sets of discrete rays chosen according to whether the point-source or diffuse components of the radiation field are being calculated. Primordial gas chemistry is modeled by solving a 9-species nonequilibrium reaction network for H, H+, He, He+, He++, H-, H2+, H2 and e-. Both radiative transfer and chemistry are incorporated into the Zeus-MP hydrodynamics code to compute halo photoexpansion timescales as well as UV escape fractions in a self-consistent manner.

The author(s) of this abstract have provided an email address for comments about the abstract: dwhalen@mamacass.ucsd.edu

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