Astronomy and Astrophysics – Astrophysics
Scientific paper
1996-11-01
Astronomy and Astrophysics
Astrophysics
16 pages with 5 figures, AAS LaTex v4.0. To appear in the Astronomical Journal, January 1997
Scientific paper
10.1086/118239
We present results from Keck I high resolution spectroscopy of the radio loud quasar PKS 0123+257 ($z_e$=2.364, V=17.5). In this object we detect Ly$\alpha$, N V 1238,1242, Si IV 1393,1402, and C IV 1548,1550 in an absorption system at a redshift of 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 ratio also clearly demonstrates that the absorbing clouds at this redshift do not fully occult the background light source along our line-of-sight. The absorption lines are positioned near the centers of the broad emission- lines and the coverage fraction of the strongest absorption lines varies inversely proportionally with the strength of the corresponding emission lines. This implies that although the absorption-line region may obscure the continuum source, it does not completely occult the broad emission-line region. This effect suggests that the lines are formed close to the QSO central region. A model is proposed in which the apparent coverage fraction derived for the weaker absorption lines may vary with the column density of the lines. Broad absorption-lines (which are known to be intrinsic) are found nearly exclusively in radio-quiet objects. Intrinsic narrow absorption lines have previously been found in radio quiet QSOs; it is therefore significant that an intrinsic absorption system has been verified in a radio loud quasar.
Barlow Thomas A.
Sargent Wallace L. W.
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