Self-sustaining Star Formation Fronts in Filaments during the Cosmic Dawn

Abstract

We propose a new model for the ignition of star formation in low-mass halos by a self-sustaining shock front in cosmic filaments at high redshifts. The gaseous fuel for star formation resides in low-mass halos that cannot cool on their own due to their primordial composition and low virial temperatures. We show that star formation can be triggered in these filaments by a passing shock wave. The shells swept up by the shock cool and fragment into cold clumps that form massive stars via thermal instability on a timescale shorter than the front’s dynamical timescale. The shock, in turn, is self-sustained by energy injection from supernova explosions. The star formation front is analogous to a detonation wave, which drives exothermic reactions powering the shock. We find that sustained star formation would typically propel the front to a speed of ∼300–700 km s −1 during the epoch of reionization. Future observations by the James Webb Space Telescope could reveal the illuminated regions of cosmic filaments, and constrain the initial mass function of stars in them.