A&A Supplement series, Vol. 127, January II 1998, 217-232
Received February 10; accepted May 12, 1997
(
)
at high resolution
,
V. D'Odorico
- S. Cristiani
- S. D'Odorico
- A. Fontana
- E. Giallongo
Send offprint request: S. Cristiani
International School for Advanced Studies, SISSA, via Beirut
2-4, I-34014 Trieste, Italy
Dipartimento di Astronomia dell'Università di Padova,
Vicolo dell'Osservatorio 5, I-35122 Padova, Italy
European Southern Observatory, Karl Schwarzschild Strasse 2,
D-85748 Garching, Germany
Osservatorio Astronomico di Roma, via dell'Osservatorio, I-00040
Monteporzio, Italy
Spectra of the 
quasar PKS 2126-158 have been obtained
in the range 
Å with a resolution 
and an average signal-to-noise ratio 
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 Ly
lines is 
km s-1.
The column density distribution can be described by a power-law
with 
.
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 
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 
and the Doppler parameter
distribution shows a modal value 
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, 
.
A trend of decreasing clustering amplitude with decreasing
column density is apparent, analogously to what has been observed
for Ly lines.
keywords: quasars: absorption lines -- quasars: individual: PKS 2126-158