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[18.11] Modelling Three Quasar Intrinsic Narrow Absorption Line Systems

J. Wu, J.C. Charlton, T. Misawa (Penn State)

We are modelling intrinsic narrow absorption line systems in three quasars (Q1700+6416, Q1009+2956, Q0130-4021) which were selected from quasar spectra obtained with the High Resolution Spectrograph (HIRES) on the Keck I telescope. The systems are known to be intrinsic because they exhibit partial covering in one or more doublet transitions. The three systems we have chosen are unusual in that they have very strong NV absorption and relatively weak Lyman-alpha absorption. We aim to understand the origin of this common type of intrinsic narrow absorption line, seen in ~ 20% of all quasars. We model these systems using the Cloudy photoionization code (Ferland 2001). The system at z=2.712538 toward Q1700+6416 has three absorption clouds. Based on comparison of our models to observed transitions, we find a metallicity of 20 times the solar value. All three clouds are found to be in relatively high ionization states with ionization parameter \log{U}= 0.3. Their hydrogen number densities are also very high. Two of the clouds have absorption profiles that can be best fit for n ~10⁸ [{\rm cm}^-3], and the other cloud requires n ~10¹³ [{\rm cm}^-3]. These results imply that the absorption clouds are all very close to the central engine, but with the different densities suggesting a range of locations. Because of the similarities of physical conditions, this gas could be located in the Broad Emission Line Region (BELR). We aim to learn if these physical conditions are typical of NV intrinsic narrow absorption line systems. We acknowledge support from NASA under grant NAG5-10817.

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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.