The Delay of Population III Star Formation by Supersonic Streaming Velocities

Understand

It has recently been demonstrated that coherent relative streaming velocities of order 30 km / s between dark matter and gas permeated the universe on scales below a few Mpc directly after recombination.

• We here use a series of high-resolution moving-mesh calculations to show that these supersonic motions significantly influence the virialization of the gas in minihalos, and delay the formation of the first stars.
• As the gas streams into minihalos with bulk velocities around 1 km / s at z ~ 20, the additional momentum and energy input reduces the gas fractions and central densities of the halos, increasing the typical virial mass required for efficient cooling by a factor of three, and delaying Population III star formation by dz ~ 4.
• Since the distribution of the magnitude of the streaming velocities is narrowly peaked around a non-negligible value, this effect is important in most regions of the universe.