Galaxies and their Gas at the Peak Epoch of Star Formation
Because faint, low mass galaxies are numerous at high redshifts, their impact on the Universe is expected to be significant. They may host a substantial fraction of the Universe's star formation, provide many of the energetic photons needed to reionize the hydrogen gas surrounding galaxies, and affect their surroundings via powerful, starburst-driven galactic outflows of gas. Because of their faintness, however, the properties of these galaxies are difficult to determine. I will discuss a variety of observations aimed at characterizing the physical conditions in low mass galaxies during the peak epoch of star formation, when the Universe was ~20% of its current age of 13.8 billion years, with particular emphasis on the study of galactic outflows in faint galaxies.