We present a detailed analysis of absorption systems along the line of sight towards QSO PKS 0237 - 233 using a high resolution spectrum of signal-to-noise ratio ( SNR ) \sim 60-80 obtained with the Ultraviolet and Visual Echelle Spectrograph mounted on the Very Large Telescope .
This line of sight is known to show a remarkable overdensity of C iv systems that has been interpreted as revealing the presence of a supercluster of galaxies .
A detailed analysis of each of these absorption systems is presented .
In particular , for the z _ { abs } = 1.6359 ( with two components of log N _ { HI } [ cm ^ { -2 } ] =18.45 , 19.05 ) and z _ { abs } = 1.6720 ( log N _ { HI } = 19.78 ) sub-Damped Ly \alpha systems ( sub-DLAs ) , we measure accurate abundances ( resp .
[ O/H ] = - 1.63 \pm 0.07 and [ Zn/H ] = - 0.57 \pm 0.05 relative to solar ) .
While the depletion of refractory elements onto dust grains in both sub-DLAs is not noteworthy , photoionization models show that ionization effects are important in a part of the absorbing gas of the sub-DLA at z _ { abs } = 1.6359 ( H i is 95 percent ionized ) and in part of the gas of the sub-DLA at z _ { abs } = 1.6359 The C iv clustering properties along the line of sight is studied in order to investigate the nature of the observed overdensity .
We conclude that despite the unusually high number of C iv systems detected along the line of sight , there is no compelling evidence for the presence of a single unusual overdensity and that the situation is consistent with chance coincidence .