summarize the main points of this paper in §\[sec:sum\].

Numerical method {#sec:gadget2}
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We model the evolution of the gas in our simulations using a modified version of the Gadget 2 smoothed particle hydrodynamics code [@springel05]. We have modified the publicly available code in several respects. First, we have added a sink particle implementation, based on the prescription in @bbp95, to allow us to follow the evolution of the gas beyond the point at which the first protostar forms. Our particular implementation is derived from the one first described in @jap05. We briefly describe the ideas behind the algorithm here. The actual numerical values used for the parameters discussed here are given later, in § \[sec:ics\].

Sink particles are not really added to the code in the sense that a new particle is introduced, but instead a normal SPH particle is turned into a sink particle once certain criteria have been met. The particle undergoes a series of tests once it has reached a threshold density. The first is to see whether the candidate SPH particle is sufficiently far away from any other sinks, measured in terms of the sink particle’s accretion radius, $r_{\rm acc}$. We adopt a conservative value 