Infrared Luminous Lyman Break Galaxies: A Population that Bridges LBGs and SCUBA Galaxies

Abstract

A deep mid- and far-infrared survey in the Extended Groth Strip (EGS) area gives 3.6 to 8\micron flux densities or upper limits for 253 Lyman Break Galaxies (LBGs). The LBGs are a diverse population but with properties correlated with luminosity. The LBGs show a factor of 30 range in indicated stellar mass and a factor of 10 in apparent dust content relative to stellar mass. About 5% of LBGs are luminous at all wavelengths with powerful emission at rest 6\micron. In the rest 0.9 to 2\micron spectral range these galaxies have stellar spectral slopes with no sign of an AGN power law component, suggesting that their emission is mainly powered by intensive star formation. Galaxies in this luminous population share the infrared properties of cold SCUBA sources: both are massive and dusty starburst galaxies at $2<z<3$; their stellar mass is larger than $10^{11} M_{\odot}$. We suggest that these galaxies are the progenitors of present-day giant elliptical galaxies, with a substantial fraction of their stars already formed at $z \approx 3$.