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N. Milutinovic, J. C. Charlton, J. Ding (Penn State), C. W. Churchill (NMSU)
Ultraviolet and optical quasar spectra provide coverage of multiple ionization states of many chemical transitions of the absorbing gaseous content of the Universe. A sample of 19 MgII absorption systems at redshifts 0.4 to 1.4 will be presented. This research surveys the gas in galaxies, as well as in gaseous clouds that produce metal absorption far from any luminous source. Photoionization and collisional ionization modeling was used to infer multiphase properties of this systems including their metallicities, densities, and temperatures.
Combining these results, we consider overall trends and seek for subcategories of MgII systems. We focus on several general issues:
i. Are the densities of the gas phases that produce MgII absorption similar or different among different MgII absorbers? This question is related to the global properties of interstellar medium gas at different locations and in galaxies with different morphological types;
ii. Is CIV gas in strong MgiI systems related to the presence or absence of galactic coronae, which are thought to be produced/maintained by star-forming processes in the disk? A CIV phase could be absent in some systems due to elliptical hosts, a low star formation rate, an outer disk line of sight, or a randomly sparse region;
iii. How common are high velocity clouds around z ~1 galaxies,and how do their properties differ from the Milky Way high velocity clouds?;
iv. What is the nature of multiple cloud weak MgII absorbers? Could they be related to dwarf galaxies, which despite a significant absorption cross section are hard to connect to other classes of absorption systems?
v. Are there cold phases of gas in absorption systems (DLAs and strong MgII absorbers) that relate to HI regions/photodissociation regions/regions surrounding molecular clouds?
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.