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Session 96 - QSO Absorption Systems.
Oral session, Wednesday, January 17
Salon del Rey South, Hilton
Important clues to the evolution of galaxies can be extracted from detailed studies of their gaseous components. The study of QSO Absorption Lines provides the only technique which can directly probe this component over a large look--back time. From high resolution QSO spectra and imaging studies of the intervening galaxies which give rise to the absorption, we can study the kinematics, chemical content, and ionization conditions (and their evolution) in galaxies with unprecedented detail.
A sample of 50 Mg II QSO absorption line profiles (0.4 \leq z \leq 1.5) at a resolution of 6 km s^-1 has been obtained with the HIRES/Keck facility. The line profiles show a remarkable variation in velocity spread, line of sight kinematics, number of clouds, and overall complexity. In 30/50 cases, other species have been detected, especially Fe II, Mn II, Ca II, and Mg I.
For 15+ of the systems, galaxies have been optical/IR imaged and spectroscopically confirmed to have the redshift seen in absorption (Steidel, Dickinson, amp; Persson, in prep). How do the kinematic, chemical, and ionization conditions in this low ionization gas depend upon host galaxy colors, rest K and B luminosities, and redshift (evolution)? I will present direct evidence for evolution of the cloud--cloud velocity dispersion of this galactic gas. I will also present a first look at how gaseous conditions in galaxies appear to correlate with their host galaxy and at what level these relations evolve with redshift.
Program listing for Wednesday