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  \subsection{The Liu Quasar Pair Catalogue}  The quasar pair catalogue sample used in this project is obtained from Lui et al 2011. The purpose \cite{Liu_2011}. This catalogue has 1286 AGN pairs in the redshift range $0.02 < z <0.33$. some  of theLui's selection  criteriais to compile (from the SDSS) a Quasar Pair catalogue  of interacting the sample AGN includes angular separation, transverse proper separation, LOS velocity offset. \cite{Liu_2011}  AGNpairs only. (Liu et al 2011)AGN pairs  that make up the parent sample are identified optically mostly optically-selected  from the spectroscopic sample of the SDSS DR7. Further selection criteria is are  applied to refine the parent sample to ensure the study of genuinely interacting AGN pairs rather than chance superpositions. Using By using  line of sight (LOS) velocity differences (or offset) where LOS velocity is the velocity meausured measured  along the line of sight of an observer, and transverse separation - the projected distance within the LOS direction - rp ,Lui selects only rp. Liu claims to significantly increase the probability that genuine  AGN pairsthat  are interacting. selected.  The choice to use projected separations rp $rp  < 100h70-1 {100h_{70})}^{-1}$  kpc to refine the sample space – remove pairs that are at low separation but are not interacting chance superpositions g  - h^-1 ${100h_{70})}^{-1}$  is the Hubble constant, which accounts for /is a measure of the expansion rate of the universe ( more details in \cite{Huchra_1992}). Lui further observes that most pairs with separation greater than 100 kpc are found to be closely separated but not interacting with one another. Selecting those with separation less than 100 kpc helps remove these points that are not a part of our sample space. It is surprising to note that 100 kpc is larger than the thresholds used in other galaxy pair studies namely (Barton et al. 2000; Ellison et al. 2008; Darg et al. 2010), but lui does not explain why 100 kpc is used as the threshold. Lui further Justifies the use a LOS velocity offset (Δv) $ \Delta v  < 600 km s-1 km.s^{-1}$  as a method to further refine the desired sample space. Observing Plotting  the distribution of (Δv) $\Delta v$  of AGN pairs (figure (2) (Figure 2  provided in Liu) shows us that that most AGN pairs in the catalogue  are found within the 300 ≲ (Δv) $300 \lsim \Delta v  < 600 km s-1 interval. km.s^{-1} $interval.  Even so, Lui et all further states that Δv range within which the pair is still interacting depends on the environment – there could be a chance that some data point were erroneously cut from the sample. Visual inspection of SDSS images for spectroscopically selected images further removes 34 AGN pairs from the parent sample. Perhaps their spectroscopic profiles do not match those of interacting pairs. What was the criteria for this- is still left unanswered.  Lui also notes possible outliers and common trends in our refined sample space. The surprising, sixteen data points with z> 0.16 ,which seem to be outliers are kept in our sample. They are said to reduce uncertainties at higher red-shifts.