Eros and Faint Red Galaxies

This chapter reviews the properties of faint IR-selected field galaxies and the extremely red color-selected populations in particular. These populations are a mix of passively evolving stellar systems and heavily obscured star-forming galaxies. The star-forming component appears to constitute 20–50% of the population depending on the magnitude and color cuts employed. The remaining objects are a mix of passively evolving ellipticals and early-type disk galaxies. The passively evolving red galaxies are strongly clustered in space and are likely the high-mass high-luminosity end of the elliptical galaxy progenitor population at redshifts between one and two. These galaxies have masses and space densities that appear to be in conflict with late-forming hierarchical galaxy-formation models. The red galaxies appear to be a population that is distinct from the moderately star-forming Lyman-Break galaxies but may be related to the starburst population at z > 2 seen in deep submillimeter surveys.