Cosmological Feedback from High-Redshift Dwarf Galaxies

We model how repeated supernova explosions in high-redshift dwarf starburst galaxies drive superbubbles and winds out of the galaxies. We compute the efficiencies of metal and mass ejection and energy transport from the galactic potentials, including the effect of cosmological infall of external gas. The starburst bubbles quickly blow out of small, high-redshift galactic disks, but must compete with the ram pressure of the infalling gas to escape into intergalactic space. We show that the assumed efficiency of the star formation rate dominates the bubble evolution and the metal, mass, and energy feedback efficiencies. With a star formation efficiency f* = 0.01, the ram pressure of infall can confine the bubbles around high-redshift dwarf galaxies with circular velocities vc ≳ 52 km s-1. We can expect high metal and mass ejection efficiencies and moderate energy transport efficiencies in halos with vc ≈ 30-50 km s-1 and f* ≈ 0.01 as well as in halos with vc ≈ 100 km s-1 and f* ≫ 0.01. Such halos collapse successively from 1-2 σ peaks in ΛCDM Gaussian density perturbations as time progresses. These dwarf galaxies can probably enrich low- and high-density regions of intergalactic space with metals to 10-3 to 10-2 Z☉ as they collapse at z ≈ 8 and z ≲ 5, respectively. They also may be able to provide adequate turbulent energy to prevent the collapse of other nearby halos, as well as to significantly broaden Ly-α absorption lines to vrms ≈ 20-40 km s-1. We compute the timescales for the next starbursts if gas freely falls back after a starburst, and find that for star formation efficiencies as low as f* ≲ 0.01 the next starburst should occur in less than half the Hubble time at the collapse redshift. This suggests that episodic star formation may be ubiquitous in dwarf galaxies.