Copyright by Athena Ranice Stacy 2011 - The University of Texas at ...

term derived from the accretion luminosity, they did not explicitly account
for molecular photodissocation by Lyman-Werner (LW) radiation from the
protostar, and they did not include the effects of ionizing radiation that will
become important once the stars have grown to larger masses (> ∼ 10 M⊙).
Whether Pop III stars can attain very large masses under feedback and
while within a multiple system is pivotal to understanding their potential for
large-scale feedback effects, such as the suppresion or enhancement of the star-
formation rate in neighboring minihalos. It also determines whether they may
be observed as gamma-ray bursts (GRBs) or extremely energetic PISNe (e.g.
Bromm and Loeb 2002, 2006; Gou et al. 2004; Belczynski et al. 2007; Stacy
et al. 2011). Furthermore, the fragmentation seen in recent work, along with
the possible ejection of low-mass Pop III stars from their host star-forming
disks (e.g. Greif et al. 2011; Smith et al. 2011), opens the possibility that
small, long-lived Pop III stars may still be observed today. This depends,
however, on uncertain factors such as the final masses reached by the ejected
stars and the amount of metal-enriched material accreted at later times while
being incorporated into larger galaxies, which could mask the stars as Pop II
(e.g. Frebel et al. 2009; Johnson and Khochfar 2011).
To further explore the range of masses possible for Pop III stars, we
perform a cosmological simulation to study the feedback effects of a protostar
on its own accretion and on further fragmentation within its host minihalo.
We initialize the simulation with sufficient resolution to follow the evolution of
the star-forming gas up to densities of 10 12 cm −3 . At this density we employ
the sink particle method, allowing us to study the subsequent disk formation
and fragmentation of the gas over the following ∼ 5000 yr. We include H2
dissociating LW feedback from the most massive star in the simulation, and
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