AAS 195th Meeting, January 2000
Session 57. Galaxies: Clusters, Lensing, and Absorption Lines
Oral, Thursday, January 13, 2000, 10:00-11:30am, Centennial IV

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[57.03] Clues to the Physical Origin of Weak MgII Absorption Systems

J. Rigby, J. Charlton, C. Churchill (Penn State)

Much has been learned about the chemical and ionization conditions of the weak MgII (EWr <0.3 {Å}) intervening absorption systems found in quasar spectra. At z~1, weak MgII systems are twice as common as the strong MgII systems known to be associated with normal galaxies, but seem not to be directly associated with bright (L*) galaxies (Churchill et al., 1999, ApJS, 120, 51.) Most do not show Lyman limit breaks, which requires N(HI)<16.8 cm-2 (Churchill et al., 1999, ApJ, submitted.) Their metallicities are greater than 3 to 10% of Solar. Single-cloud weak MgII systems outnumber double-cloud systems by at least 4:1. This requires a covering factor less than ~.2, so that lines of sight, on average, encounter only one absorber.

Most weak systems contain at least two phases of gas: a high-ionization component with Doppler parameter b~50 km/s, and a low-ionization component with 2We acknowledge NSF (AST--9617185) and NASA (NAG 5--6399) grants. J. Rigby was supported by an NSF REU supplement.

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The author(s) of this abstract have provided an email address for comments about the abstract: jrigby@astro.psu.edu

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