Star Formation at Very Low Metallicity. IV. Fragmentation Does Not Depend on Metallicity for Cold Initial Conditions

Understand

Primordial star formation appears to result in stars at least an order of magnitude more massive than modern star formation.

• It has been proposed that the transition from primordial to modern initial mass functions occurs due to the onset of effective metal line cooling at a metallicity Z/Z_sun = 10^{-3.5}.
• However, these simulations neglected molecular hydrogen cooling.
• We perform simulations using the same initial conditions, but including molecular cooling, using a complex network that follows molecular hydrogen formation and also directly follows carbon monoxide and water.