The Rise of the First Stars: Supersonic Streaming, Radiative Feedback,
  and 21-cm Cosmology
  Understanding the formation and evolution of the first stars and galaxies
represents one of the most exciting frontiers in astronomy. Since the universe
was filled with hydrogen atoms at early times, the most promising probe of the
epoch of the first stars is the prominent 21-cm spectral line of hydrogen.
Current observational efforts are focused on the cosmic reionization era, but
observations of the pre-reionization cosmic dawn are also promising. While
observationally unexplored, theoretical studies predict a rich variety of
observational signatures from cosmic dawn. As the first stars formed, their
radiation (plus that from stellar remnants) produced significant cosmic events
including Lyman-alpha coupling at z~25, and early X-ray heating. Much focus has
gone to studying the angle-averaged power spectrum of 21-cm fluctuations.
Additional probes include the global (sky-averaged) 21-cm spectrum, and the
line-of-sight anisotropy of the 21-cm power spectrum. A particularly striking
signature may result from the recently recognized effect of a supersonic
relative velocity between the dark matter and gas. Work in this field, focused
on understanding the whole era of reionization and cosmic dawn with analytical
models and numerical simulations, is likely to grow in intensity and
importance, as the theoretical predictions are finally expected to confront
21-cm observations in the coming years. [Abridged]
