Instability of Supersonic Cold Streams Feeding Galaxies IV: Survival of Radiatively Cooling Streams

Understand

We study the effects of Kelvin Helmholtz Instability (KHI) on the cold streams that feed massive halos at high redshift, generalizing our earlier results to include the effects of radiative cooling and heating from a UV background, using analytic models and high resolution idealized simulations.

• We currently do not consider self-shielding, thermal conduction or gravity.
• A key parameter in determining the fate of the streams is the ratio of the cooling time in the turbulent mixing layer which forms between the stream and the background following the onset of the instability, $t_{\rm cool,mix}$, to the time in which the mixing layer expands to the width of the stream in the non-radiative case, $t_{\rm shear}$.
• This can be converted into a critical stream radius, $R_{\rm s,crit}$, such that $R_{\rm s}/R_{\rm s,crit}=t_{\rm shear}/t_{\rm cool,mix}$.