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R. S. Lynch, J. C. Charlton (Penn State)
Lynch et al. (ApJ submitted) surveyed 18 UVES/VLT quasar spectra, obtained from the ESO archive, to search for weak MgII \lambda \lambda doublets (defined to have Wr(2796) \le 0.3 Å) in the redshift range 1.4 < z < 2.4, and found 9 such systems. The redshift path density dN/dz = 1.06 ±0.12 is lower than that observed at z ~1, suggesting that at z ~2 we are studying weak absorbers before the peak epoch of their incidence. We present photoionization models of 9 systems at z ~2 given by the Cloudy photoionization code (Ferland 2001). Similar models were discussed for 15 systems at z ~1 in Rigby et al. (2001). They found that the systems are generally optically thin in neutral hydrogen and have near solar, or even supersolar metallicities. Many of the systems consist of two phases of gas, one that gives rise to low ionization MgII absorption, and one that gives rise to high ionization CIV absorption. Our results at z ~2 are similar, with all of our systems likely exhibiting the same two-phase structure, and metallicities \log Z\sun \ge -1.0. Although there are not as many weak MgII absorbers at z ~2 than at z ~1, their properties appear similar. This work was funded by the Nation Science Foundation grant NSF AST-07138 and by an NSF REU supplement.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.