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A&A Supplement series, Vol. 127, January II 1998, 217-232

Received February 10; accepted May 12, 1997

The absorption spectrum of the QSO PKS tex2html_wrap_inline1949 (tex2html_wrap_inline1951) at high resolutiongif,gif

V. D'Odoricotex2html_wrap2009 - S. Cristianitex2html_wrap2011 - S. D'Odoricotex2html_wrap2013 - A. Fontanatex2html_wrap2015 - E. Giallongotex2html_wrap2015

Send offprint request: S. Cristiani

tex2html_wrap2019  International School for Advanced Studies, SISSA, via Beirut 2-4, I-34014 Trieste, Italy
tex2html_wrap2021  Dipartimento di Astronomia dell'Università di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy
tex2html_wrap2023  European Southern Observatory, Karl Schwarzschild Strasse 2, D-85748 Garching, Germany
tex2html_wrap2025  Osservatorio Astronomico di Roma, via dell'Osservatorio, I-00040 Monteporzio, Italy


Spectra of the tex2html_wrap_inline1959 quasar PKS 2126-158 have been obtained in the range tex2html_wrap_inline1963 Å with a resolution tex2html_wrap_inline1965 and an average signal-to-noise ratio tex2html_wrap_inline1967 per resolution element. The list of the identified absorption lines is given together with their fitted column densities and Doppler widths. The modal value of the Doppler parameter distribution for the Lytex2html_wrap_inline1969 lines is tex2html_wrap_inline1971 km s-1. The column density distribution can be described by a power-law tex2html_wrap_inline1975 with tex2html_wrap_inline1977.

12 metal systems have been identified, two of which were previously unknown. In order to make the column densities of the intervening systems compatible with realistic assumptions about the cloud sizes and the silicon to carbon overabundance, it is necessary to assume a jump beyond the He II edge in the spectrum of the UV ionizing background at tex2html_wrap_inline1979 a factor 10 larger than the standard predictions for the integrated quasar contribution.

An enlarged sample of C IV absorptions (71 doublets) has been used to analyze the statistical properties of this class of absorbers strictly related to galaxies. The column density distribution is well described by a single power-law, with tex2html_wrap_inline1981 and the Doppler parameter distribution shows a modal value tex2html_wrap_inline1983 km s-1. The two point correlation function has been computed in the velocity space for the individual components of C IV features. A significant signal is obtained for scales smaller than 200- 300 km s-1, tex2html_wrap_inline1991. A trend of decreasing clustering amplitude with decreasing column density is apparent, analogously to what has been observed for Lytex2html_wrap_inline1969 lines.

keywords: quasars: absorption lines -- quasars: individual: PKS 2126-158

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