Lyman-Break Galaxies

In this paper we review the properties of Lyman-break galaxies, namely starburst galaxies at high redshifts, approximately in the range 2.5 < z < 5, identified by the colors of their far ultraviolet spectral energy distribution around the 912 Å Lyman continuum discontinuity. The properties of forming galaxies in the young universe are very important to constrain the history of galaxy evolution and the formation of the Hubble sequence, and until recently, they have remained largely unexplored. The Lyman-break technique has broken an impasse in the exploration of galaxies at high redshift that lasted for about two decades, and within a few years has yielded large and well-controlled samples of star-forming, but otherwise normal, galaxies at z > 2.5, including ∼1000 spectroscopic redshifts and another few thousands of robust candidates. This dataset has allowed us an unprecedented look at fundamental properties of galaxies at 20% of the Hubble time or less. In this paper, we discuss the nature of the Lyman-break galaxies and their properties, including star-formation rate, stellar and total mass, chemical abundance, morphology, and interstellar medium (ISM) kinematics, and outline their contribution to the stellar content of the universe and their connection to the galaxies observed in the present-day universe. We also discuss what the properties of these galaxies, in particular their spatial clustering, imply about the mechanisms of galaxy formation and about the relationship between the underlying distribution of dark matter and the activity of star formation.