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

Chapter 3
Mass Growth Under Protostellar Feedback 1
3.1 Introduction
Previous work has found that Pop III stars begin as very small proto-
stars of initial mass ∼ 5 × 10 −3 M⊙ (Omukai and Nishi 1998; Yoshida et al.
2008). Continued accretion onto the protostar over time ultimately leads to
stars significantly larger than the initial seeds (e.g. Omukai and Palla 2003;
Bromm and Loeb 2004). The final mass reached by Pop III stars therefore
depends on the rate and duration of the accretion. Early numerical studies
found that Pop III stars are likely to reach very high masses (> ∼ 100 M⊙; e.g.
Abel et al. 2002; Bromm et al. 2002). The lack of metal and dust cooling
in primordial gas leads to higher temperatures and greater accretion rates as
compared to current star-forming regions such as the giant molecular clouds
within the Milky Way.
The accretion history of Pop III stars depends critically on the radiative
feedback exerted during their growth phase, an effect not included in the
earliest three-dimensional simulations. The strength of protostellar feedback
in turn hinges upon the three-dimensional structure of the surrounding gas.
For instance, Omukai and Inutsuka (2002) find that for spherically symmetric
accretion onto an ionizing star, the formation of an H ii region in fact does not
1 Large portions of this chapter have been submitted for publication in MNRAS. Reproduced
by permission of John Wiley and Sons.
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