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T. Misawa, J.C. Charlton, M. Eracleous (Penn State University), R. Ganguly (University of Wyoming), D. Tytler, D. Kirkman, N. Suzuki, D. Lubin (UCSD)
We present a large database of intrinsic narrow absorption lines (NALs), which we have separated from intervening NALs using covering factor analysis. We have searched 40 Keck/HIRES spectra of quasars at z=2-4, and found 150 absorption systems that contain 124 C IV, 12 N V, and 50 Si IV NALs. We classified the resulting systems into 39 intrinsic and 111 intervening/unclassified systems. The fraction of C IV NALs to be classified as intrinsic is 11-19 percent, which is about half of the value statistically estimated in Richards et al. (1999). The two results are consistent with each other if not all intrinsic C IV NALs have partial coverage. Due to the Lyman-alpha forest, we can only perform covering factor analysis for associated N V NALs (i.e., those within 5000 km/s of the quasar redshift); we find that 75 percent of them show the signature of partial covering. The intrinsic N V NALs tend to have small covering fractions (less than 0.5) as compared to intrinsic C IV NALs, whose covering factors can be close to 1. This suggests different sizes or velocity structures of the N V and C IV absorbers, or different sites of origin. The minimum fraction of quasars to have one or more intrinsic NALs is approximately 50 percent, implying that that at least half of the solid angle around a typical quasar is covered by intrinsic absorbers or that at least half of all quasars are fully covered. About half of the intrinsic C IV NAL systems are also detected in low-ionization transitions such as C II and Si II. This fraction is much higher than in LoBALs (about 15 percent). The similar velocity structure of the high- and low-ionization absorption lines accompanying intrinsic C IV NAL systems suggests that the low ionization gas is part of the quasar outflow, and not of the host galaxy. We acknowledge support from NASA grant NAG5-10817.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.