Rajib Ganguly, Chris Churchill, Jane Charlton
This slideshow presents our poster from the 1998
winter meeting of the AAS (191).
Abstract Preview of Slideshow First Slide Return to Group Page
We decompose a system at z=1.9373 in the line of sight to Q1222+228 into separate Voigt profiles interpreted to be single phase clouds. Coverage of the HIRES/KECK spectra allowed detection of C IV, Si II, Si IV, Al II and Al III. The decomposition of Al II and Al III allows the determination of the ionization parameter as a function of the H I column density and the metalicity. One cloud near the center of the profile is found to have Al II and Al III column densities which, in conjunction with a Si II column density limit and assuming a solar abundance pattern , predict a Si IV column density that is 0.66 dex higher than the observed Si IV column density. This points towards either a depletion of the Si or an enrichment of Al in this cloud. Explanation of the anomalous abundance pattern cannot rely on dust depletion since in fact Al depletes more readily than Si. We compare this unusual Al--rich cloud to another more ordinary cloud in the same system, to another CIV system with detected Al found in our HIRES/KECK data, and to a damped system from Lu et al. (1996) which appears to exhibit the same phenomenon. We speculate as to the processes/conditions that could give rise to such an Al--rich abundance pattern.
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