Search Techniques for Distant Galaxies

How and when do galaxies form? Studies of the microwave background radiationreveal that the Universe is spectacularly homogenous at redshift z~1000.Observations of the local Universe reveal that by z=0 much of the luminousmatter has condensed into mature, gravitationally-bound structures. One of theprimary challenges to astronomers today is to achieve a robust understanding ofthis process of galaxy formation and evolution. Locating and studying younggalaxies at large look-back times is an essential aspect of this program. Wereview the systematic observational techniques used to identify galaxies atearly cosmic epochs. In the past few years, the study of normal, star-forminggalaxies at z>3 has become possible; indeed, successful methods have beendeveloped to push the frontier past z=5. We are now directly observingindividual galaxies within a Gyr of the Big Bang. We present a detailed reviewof the many search methods used for identifying distant galaxies, consider thebiases inherent in different search strategies, and discuss early results ofthese studies. We conclude with goals for future studies at the start of the21st century.Comment: 53 pages, 14 figures; invited review to appear in Publications of the Astronomical Society of the Pacific (Dec 1999