AAS 197, January 2001
Session 66. When the Universe was Mostly Gas
Oral, Tuesday, January 9, 2001, 1:30-3:00pm, Royal Palm 3/4

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[66.05] The Absorbers Toward CSO 118: Hierarchical Clustering at z~3, or an Intrinsic Absorption Complex?

R. Ganguly, J. C. Charlton (Penn State University)

We present a high signal-to-noise spectrum of the {z\rm em=2.97} radio-quiet quasar CSO 118 observed by the Hobby-Eberly Telescope with the Marcario Low Resolution Spectrograph. The R~1300 spectrum covers the wavelength range {4300Å-7300Å} which includes the C IV, Si IV, N V, and Ly {\alpha} emission lines and well as the Ly {\alpha} forest down to z\approx2.5. We detect a complex of six C IV--selected absorbers in the range {2.65\rm r({\rm C IV})<0.47Å}. The redshift path density of these absorbers is dN/dz\approx24, three times greater than average as reported by Tripp, Lu, & Savage (1996). This implies two possibilities for the origin of these systems: (1) photons may have passed through a region of space where gas clumps are hierarchically collapsing as suggested by Kirkman & Tytler (1999); or (2) this is a multiple absorption complex due to gas intrinsic to the QSO.

The line-of-sight velocity dispersion of the complex is {~.5\times104~km s-1}, much larger than the velocity dispersion of typical groups of galaxies ({\sigma\rm v~00~km s-1}). On the other hand, if these absorbers constitute ejected material, the ejection velocities range from {~300~km s-1} to {~.3\times104~km s-1}. Intrinsic narrow velocity dispersion absorbers have been reported with ejection velocities as high as {~\times104~km s-1}. It is also not unusual to have multiple absorption systems intrinsic to a QSO. Broad absorption lines, whose troughs extend from the QSO emission redshift to {~.1c}, are typically accompanied by their narrow kin.

In addition, we will present evidence that the three pairs of systems may be line-locked. If verified, this would enforce the intrinsic origin of these systems. We gratefully acknowledge the support of two grants: NSF grant AST96-17185 and NASA grant NAG5-6399.

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

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