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Session 5 - High Luminosity AGN.
Display session, Monday, June 10
We present results from Keck I service observations of the radio loud quasar PKS 0123+2543 (z_e=2.358, V=17.5). We selected this object in order to study intrinsic QSO absorption line systems, since it had been reported to have an absorption system with z_a > z_e. It has been demonstrated previously (Barlow 1995, BAAS 27, 872) that high resolution (\sim 6 km/s FWHM) spectra of QSO absorption lines can be used to help distinguish narrow intrinsic and intervening systems.
In this object, we detect Ly\alpha, N V \lambda\lambda1238,1242, Si IV \lambda\lambda1393,1402, and C IV \lambda\lambda1548,1550 in an absorption system at z_a=2.369. The Ly\alpha line has a square-bottomed profile suggesting a high column density of gas, yet the line does not reach zero intensity. The resolved C IV doublet clearly demonstrates that the absorbing clouds do not cover the background light source since the calculated optical depth assuming complete coverage is not 2:1.
The absorption lines are positioned near the center of the broad emission-lines and the coverage factor of the different ions varies with the strength of the broad emission lines. This implies that although the absorption region may obscure the continuum source, it does not completely cover the broad emission-line region. This effect suggests that the lines are close to the QSO central region (intrinsic to the QSO).
Broad absorption-lines (which are known to be intrinsic) are found nearly exclusively in radio-quiet objects. Although intrinsic narrow absorption lines have previously been found in radio quiet QSOs (Hamann et al. 1995, ApJ 443, 606), it is significant that an intrinsic absorption system has been found in a radio loud quasar.
Program listing for Monday