AAS 195th Meeting, January 2000
Session 18. QSO Absorption Lines
Display, Wednesday, January 12, 2000, 9:20am-6:30pm, Grand Hall

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[18.01] On the Origin of Intrinsic UV Narrow Absorption Lines in Low-Redshift QSOs I.: A Survey

N.A. Bond, R. Ganguly, J.C. Charlton, C.W. Churchill, M. Eracleous, W.N. Brandt (Penn State)

In this first of a two-poster display, we present the results from a survey of associated narrow absorption systems in a low-redshift, optically-selected sample of 64 QSOs from the HST Quasar Absorption Line Key Project. Sixteen CIV-selected systems were detected within {5000~km/s} of the QSO emission redshift at a 3-sigma sensitivity. We present velocity aligned plots of all transitions detected at the absorber redshift. In ten of the systems, we detect higher ionization lines from either NV or OVI which are commonly found in intrinsic absorbers (Barlow & Sargent 1997). We statistically determine the fraction of the 16 systems that are likely to be intrinsic to the QSO based on the expected number of intervening systems in the same redshift path. In the second poster (Ganguly et al., this session), we compile multiwavelength properties of the QSOs, report the results of a multivariate analysis, and discuss possible interpretations.

The recent identification of several high-redshift QSOs that host intrinsic narrow absorption lines (NALs) (e.g. Q~2343+125, UM~675, PG~1222+228) has raised the need to consider the physical origin of this gas. Unfortunately, ground-based, high-redshift surveys for CIV-selected NALs have yielded inconsistent results. In particular, studies done with radio-selected samples (e.g. Foltz et al.~1986, Anderson et al.~1987) have shown a statistical excess of strong (i.e. high equivalent width) systems within {5000~km/s} of the QSO emission redshift. This excess indicates the presence of absorption arising from gas intrinsic to the QSO environment. However, optically-selected samples (Sargent et al.~1988, Sargent et al.~1989) have shown no such excess. A study of low-redshift QSOs, for which multiwavelength properties can be obtained, may yield the underlying mechanism for the formation of intrinsic NALs and a solution to the high-redshift disparity.

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

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