Our Second Look at the Immature Universe: The Infrared View

The long-awaited promise of studying high-redshift galaxies at long wavelengths has been partially eclipsed by progress at optical wavelengths, mostly because of the number of available pixels. It is nonetheless essential to study optically selected high-redshift galaxies at wavelengths longward of 1\mic, for several reasons. One of the indications from such studies to date is that interstellar dust (as an absorber of UV photons and re-emitter of IR photons) plays an energetically significant role at high redshifts, just as it does in present-day star-forming galaxies. This also provides a strong motivation for new searches which detect high-redshift galaxies based on IR observations. Some of these are already succeeding in clarifying our view of galaxy evolution in the Immature Universe.