QSO Absorption Lines and Cosmology

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QSO absorption lines and comsologyWallace SargentAbsorption lines observed in the spectra of quasars provide a way to study the interstellar gas in galaxies and gas in the intergalactic medium along the line of sight to the quasar. Dr. Sargent is extending observations and analyses in a program of quasar absorption line studies. He is using the High Resolution Echelle Spectrograph (HIRES) on the Keck 10 meter telescopes. There are three objectives: (1) to study the evolution of the heavy element content of galaxies and the intergalactic medium as a function of cosmic time from redshift about 5 (when the universe was about 10% of its present age) forward to the present epoch; (2) to study the structure of the gas in galaxies and intergalactic space on scales ranging from 10pc to 100kpc using the absorption lines observed in multiple images of gravitationally lensed quasars or quasar pairs, and (3) to study the cosmical evolution of the meta-galactic flux of UV radiation capable of ionizing hydrogen. This investigation addresses the relative importance of the contributions of quasars and galaxies to the ionizing flux at different cosmic epochs.