Design and scaling of an Omega-EP experiment to study cold streams feeding early galaxies*

Galaxies form in dark matter halos. Massive galaxies forming around redshifts of z=1 are believed to grow by "hot" accretion: gas accretes semi-spherically, establishing a shock that heats up infalling gas, which then slowly cools and shrinks to the disc. Smaller, younger galaxies forming at  z=2-4 are believed to be fed by cold streams: cold, dense gas delivered straight to the disc by highly collimated filamentary flows. However, the most prolific star forming galaxies in the universe are young but massive, with cold, dense filaments penetrating its hot, diffuse halo. 

Such a flow is likely Kelvin-Helmholtz (KH) unstable. Significant KH evolution as well as collapse of the filament by a shock-heated background may disrupt the cold stream and mark the transition from cold to hot accretion. We present here our design and scaling of an Omega EP laser experiment to study this process in the lab.