Investigation of Gas in Protogalaxies

University Of California-San Diego, La Jolla CA

Investigators

Abstract

AST- 0071257 Wolfe The goals of this proposal are to study the properties and implications of the damped Lyman-alpha absorption systems seen in quasar spectra. The PI's earlier work suggests that Ly-alpha systems are the gaseous progenitors of most normal galaxies with kinematics and ionization levels which indicate absorption in moving, presumably merging, clumps rather than smooth disks. The PI has started a numerically-intensive simulation program to examine consistency between the observations and cosmological parameters. The object of this proposal is to find and observe the ancestors of typical current galaxies; i.e., protogalaxies. Current theories, (for example, cold dark matter cosmologies (CDM)), predict that most protogalaxies were much less massive than current galaxies. Thus, the starlight emitted by exceedingly distant protogalaxies is too faint to detect by conventional techniques. By contrast the surveys for neutral gas discussed in this proposal are capable of detecting low-mass objects. Since stars in current galaxies have formed out of interstellar gas for the past 10 billion years, most of the ordinary matter in protogalaxies must have been gas. We detect the gas in absorption against the bright light emitted by even more distant quasars. The principal signature of gaseous protogalaxies is strong absorption in the hydrogen Lyman - alpha line. In principle we can detect low-mass objects since the absorption strength of the gas is insensitive to variations of the mass of the protogalaxy. In this work, the PIs will use the two Keck 10 m telescopes to test predictions of CDM, studying the velocity structure of the neutral and ionized gas to determine whether gas motions are generated by rotating disks or some other mechanism. and measuring the abundance of heavy elements in order to trace chemical enrichment of galaxies over cosmic time scales. and searching for emission of starlight from galaxies associated with the absorbing gas. These observations will be compared with numerical simulations of the formation of damped Lyman - alpha systems in CDM cosmologies. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC). ***