The basic properties of the first stars have been well established.

Form in 105 to 106 Mminihalos

Redshifts of 20 to 3

Gas cools via H2

Stacy et al. 2010

Recent work has revised this picture somewhat.

Recent 2D calculations have shown that protostellar feedback limits the first stars to nearer 50 M Hosokawa et al. (2011)

Recent 3D simulations have shown that significant fragmentation occurs. Stacy et al. (2010), Greif et al. (2011), Clark et al.

(2011) Broader Initial Mass Function

Recent work has revised this picture somewhat.

Recent 2D calculations have shown that protostellar feedback limits the first stars to nearer 50 M Hosokawa et al. (2011)

Recent 3D simulations have shown that significant fragmentation occurs. Stacy et al. (2010), Greif et al. (2011), Clark et al.

(2011) Broader Initial Mass Function

The disk around the central protostar fragments, but only just.

The Toomre Q parameter of these disks is close to unity.

So, they are just barely unstable, and external heating could suffice to make them remain stable.

Greif et al. (2012)

We are investigating how much external heating would be required to stabilize the disk.

We are focusing on two mechanisms:X-raysCosmic Rays

To do this, we include additional heating and ionizations terms in a cosmological simulation.Using GADGET-2 SPH codeAdd in an external X-ray and CR background

based on analytic estimates.

We start with the initial conditions from Athena’s 2010 paper.

We start with the initial conditions from Athena’s 2010 paper.

We run an initial simulation without any background for comparison.

We run an initial simulation without any background for comparison.

We run an initial simulation without any background for comparison.

We see the formation of a disk, and a binary system emerges.

Range: 109 to 1012 cm-3

We see the formation of a disk, and a binary system emerges.

Range: 109 to 1012 cm-3

We see the formation of a disk, and a binary system emerges.

Range: 109 to 1012 cm-3

Two sink particles form.

TimelineCurrently in the process of adding the external

X-ray background into the code.The Cosmic Ray background is next.We hope to submit this paper mid-semester

(Spring 2013).Begin a new project Spring 2013.Expected graduation: Spring 2015