Annu. Rev. Astron. Astrophys. 2005. 43: 677-725 Copyright © 2005 by Annual Reviews. All rights reserved

Reprinted with kind permission from Annual Reviews, 4139 El Camino Way, Palo Alto, California, USA

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Abstract. The Early Universe Molecular Emission Line Galaxies (EMGs) are a population of galaxies with only 36 examples that hold great promise for the study of galaxy formation and evolution at high redshift. The classification, luminosity of molecular line emission, molecular mass, far-infrared (FIR) luminosity, star formation efficiency, morphology, and dynamical mass of the currently known sample are presented and discussed. The star formation rates derived from the FIR luminosity range from about 300 to 5000 M year^-1 and the molecular mass from 4 × 10⁹ to 1 × 10¹¹ M. At the lower end, these star formation rates, gas masses, and diameters are similar to those of local ultraluminous infrared galaxies, and represent starbursts in centrally concentrated disks, sometimes, but not always, associated with active galactic nuclei. The evidence for large (> 5 kpc) molecular disks is limited. Morphology and several high angular resolution images suggest that some EMGs are mergers with a massive molecular interstellar medium in both components. A critical question is whether the EMGs, in particular those at the higher end of the gas mass and luminosity distribution, represent the formation of massive, giant elliptical galaxies in the early Universe. The sample size is expected to grow explosively in the era of the Atacama Large Millimeter Array (ALMA).

Table of Contents

• INTRODUCTION
• DEFINING THE EMGs
• Luminosities: Basic Relations
• From CO Luminosity to Molecular Mass
• Classification of the EMGs
• Examples of EMGs
• DISCUSSION
• Molecular Gas Mass and Star Formation Efficiency
• Star Formation and Gas Depletion Lifetime
• HCN, [CI], & [CII] Emission
• Masses, Sizes, & Evolutionary Destiny
• OBSERVATIONAL PROSPECTS
• REFERENCES