NSF Young Investigator: The Evolution of Normal Galaxies

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9457446 Steidel Over the course of the next several years, a number of inter-related projects will be pursued which address the broad question of the history of "normal", Milky-Way-like galaxies from the epoch of their formation to the present time. The studies are based on a combination of the technique of quasar absorption line spectroscopy and more conventional optical and near-infrared imaging and spectroscopy of very faint, distant galaxies. The objects for study are selected on the basis of their having produced hydrogen and metallic absorption lines in the spectra of even more distant, background quasars. High resolution spectroscopy of the quasars yields extremely detailed physical information on the galaxies producing the absorption, even for galaxies whose mere detection (using conventional methods) strains our technological capabilities at the present time. Samples of galaxies, selected in essence by their gas cross-section, are constructed without any biases related to the nature of stellar radiation being emitted by the galaxies as a function of time. The samples represent a very large range of cosmic epochs, from times when the Universe was only 10% of its current age, to the present. One then combines this information with data that is obtained from direct identification of the galaxies producing the absorption line systems using imaging and low-dispersion galaxy spectroscopy in the optical and the near-infrared. These latter data provide information on the stellar populations, luminosities, and geometrical orientations with respect to the line of sight to the quasars. In total, then, one obtains information on the chemical composition, gas-phase structure, kinematics, luminosity distribution, ionization state, space density, and clustering properties of galaxies as a function of time. The marriage of these methods, all of which can be pursued using currently existing instrumentation on large ground-based telescopes, allows the construct ion of a detailed history of normal galaxies since the time of their formation. Galaxy formation and evolution theories are at present largely unconstrained by observations, and it is the intent of this research effort to place the subject on a firm empirical footing. This award is to recognize an outstanding young faculty member in science and engineering. The award will enhance the career of the faculty member by providing flexible support for research and educational activities. Cooperation with industry and institutions that support research and education is encouraged.