At modest radii from the centre of galaxy clusters , individual galaxies may be infalling to the cluster for the first time , or have already visited the cluster core and are coming back out again .
This latter population of galaxies is known as the backsplash population .
Differentiating them from the infalling population presents an interesting challenge for observational studies of galaxy evolution .
To attempt to do this , we assemble a sample of 14 redshift- and spatially-isolated galaxy clusters from the Sloan Digital Sky Survey .
We clean this sample of cluster-cluster mergers to ensure that the galaxies contained within them are ( to an approximation ) only backsplashing from the centre of their parent clusters and are not being processed in sub-clumps .
By stacking them together to form a composite cluster , we find evidence for both categories of galaxies at intermediate radii from the cluster centre .
Application of mixture modelling to this sample then serves to differentiate the infalling galaxies ( which we model on galaxies from the cluster outskirts ) from the backsplash ones ( which we model on galaxies in the high density core with low velocity offsets from the cluster mean ) .
We find that the fraction of galaxies with populations similar to the low velocity cluster core galaxies is f = -0.052 R / R _ { virial } +0.612 \pm 0.06 which we interpret as being the backsplash population fraction at 1 < R / R _ { virial } < 2 .
Although some interlopers may be affecting our results , the results are demonstrated to be in concordance with earlier studies in this area that support density-related mechanisms as being the prime factor in determining the star formation rate of a galaxy .