The goal of the Complete Optical and Radio Absorption Line System ( CORALS ) survey is to quantify the potential impact on QSO absorber statistics from dust in intervening galaxies .
Dust may introduce a selection bias in surveys which are based on magnitude limited QSO samples , leading to an underestimate of absorber number density , n ( z ) .
Here we present the results of the second phase of the CORALS survey which extends our previous work on z > 1.8 damped Lyman \alpha systems ( DLAs ) to search for strong metal line systems ( candidate DLAs ) in the range 0.6 < z < 1.7 .
We have identified 47 Mg II systems with rest frame equivalent widths EW ( Mg ii \lambda 2796 ) > 0.3 Å in our sample of 75 radio-selected quasars .
The total redshift path covered by the survey is \Delta z = 35.2 , 58.2 and 63.8 for EW ( Mg ii \lambda 2796 ) > 0.3 , 0.6 and 1.0 Å thresholds respectively ( 5 \sigma ) .
Our principal and most robust result is that the n ( z ) of low redshift Mg ii systems determined for the CORALS survey is in excellent agreement with that of optically-selected , magnitude limited QSO samples .
We use empirically determined Mg ii equivalent width statistics to estimate the likely number of DLAs in this sample .
The statistically inferred number density of DLAs , n ( z ) = 0.16 ^ { +0.08 } _ { -0.06 } , is consistent with other low redshift samples , although the large 1 \sigma error bars permit up to a factor of 2.5 more DLAs in CORALS .
However , confirmation of the DLA candidates , precise evaluation of their n ( z ) and measurement of their H I column densities awaits UV observations with the Hubble Space Telescope .
Finally , we report an excess of intermediate redshift Mg ii systems observed towards bright QSOs which could be due to a lensing amplification bias .
However , there is also evidence that this excess could simply be due to more sensitive EW detection limits towards brighter QSOs .
We also emphasize that absorber statistics determined from magnitude limited surveys reach a steady value if the completeness limit is significantly fainter than the fiducial value of the quasar luminosity function .