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J. Ding, J. C. Charlton (Penn State University)
Quasar absorption-line systems, selected by MgII absorption, sample various types of galaxies (e.g. giant, dwarf, and proto-galaxies) at a wide range of redshifts. Absorption produced by some combination of disk interstellar medium (ISM), coronal gas, and high-velocity clouds reveals a wealth of information on kinematics, chemical composition, and ionization state of intervening gas. Here, I am presenting the results of modeling nearly 20 MgII-selected systems over the redshift range 0.5 < z < 1.5 and their implication on the formation and evolution of galaxies over this intermediate redshift epoch.
At z~1, luminous galaxies ( > 0.05L* galaxies, where L* is the Schechter luminosity) are traced by strong MgII absorbers (those with rest-frame equivalent width Wr(MgII 2796) > 0.3 Å). Many of these galaxies are found to have large spatial variations of density in their disk ISM. In a few cases, small, dense pockets, similar to damped Lya systems in size and density, are also present. A variety of kinematic structures are displayed in the corona/halo gas of these galaxies, indicating different morphologies, evolutionary stages, and/or ionizing mechanisms. Satellite clouds, sometimes found around strong absorbers, could represent the Milky Way high-velocity clouds at higher redshifts. Weak MgII absorbers, constituting the majority ( > 65%) of the entire MgII absorber population at 0.5 < z < 1, make up much of the high column density end of the Lya forest (those with log N(HI) > 15). Single-cloud, weak absorbers usually have high metallicities and could be potential tracers of the missing galaxies in dark matter haloes predicted in the cold dark matter simulations. Multiple-cloud, weak MgII absorbers have an indicated origin in either dwarf/low-surface-brightness galaxies or the outskirts of giant galaxies.
This project is funded by the National Science Foundation and by NASA through the STScI and LTSA program.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.