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J. Charlton, R. Mellon, J. Rigby, C. Churchill (Penn State)
We present simulated STIS spectra of four MgII systems along the line of sight toward the quasar PG~1634+706. For this bright quasar, very high signal--to--noise Space Telescope Imaging Spectrograph (STIS) spectra at high resolution (R=10~km/s) were recently obtained (1999 May and June), covering 1850 to 3100 Angstroms. However, these data are still proprietary in the HST archive, and we deliberately present this poster without knowledge of the spectra.
The primary goal of this study is to conduct a fair test of the validity of a photoionization modeling technique that is applicable when a combination of high and low resolution spectra are available for various chemical transitions. We apply constraints from: 1) High Resolution Spectrograph (HIRES/Keck I) (6.6~km/s) profiles of low ionization species, MgII and FeII; and 2) an archival, low resolution (R=230~km/s) HST/FOS (Faint Object Spectrograph) spectrum covering Ly\alpha, Ly\beta, SiII, SiIII, SiIV, CII, CIII, CIV, NV, and OVI. Although the high resolution STIS spectra of PG~1634+706 will soon be released, it is only practical to obtain high resolution UV spectra for a handful of the brightest quasars. The technique that we have developed, if demonstrated to be valid, will be applicable for large statistical studies of multiphase absorption and galaxy properties.
The four MgII absorbers along the PG~1634+706 line of sight exhibit a variety of MgII kinematic structures and higher ionization phases. They include one single cloud, weak MgII absorber without detected CIV in the FOS spectrum, and another with strong CIV absorption. Based on our modeling, we predict that the most unusual system, at z=1.0414, will have at least two distinct components in the CIV profile, one centered on the MgII absorption, and the other (without detected MgII) offset 200~km/s to the blue.
We acknowledge NASA (NAG 5--6399) and the NSF (AST--9617185). R. Mellon and J. Rigby were 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: charlton@astro.psu.edu