The influence of streaming velocities and Lyman-Werner radiation on the formation of the first stars

Understand

The first stars in the Universe, the so-called Population III stars, form in small dark matter minihaloes with virial temperatures $T_{\rm vir} < 10^{4}$~K.

• Cooling in these minihaloes is dominated by molecular hydrogen (H$_{2}$), and so Population III star formation is only possible in those minihaloes that form enough H$_{2}$ to cool on a short timescale.
• As H$_{2}$ cooling is more effective in more massive minihaloes, there is therefore a critical halo mass scale $M_{\rm min}$ above which Population III star formation first becomes possible.
• Two important processes can alter this minimum mass scale: streaming of baryons relative to the dark matter and the photodissociation of H$_{2}$ by a high redshift Lyman-Werner (LW) background.