We present BV photometry of four Sagittarius dwarf spheroidal galaxy globular clusters : Arp 2 , NGC 5634 , Palomar 12 , and Terzan 8 , obtained with the Danish telescope at ESO-La Silla .
We measure the structural parameters of the clusters using a King profile fitting , obtaining the first reliable measurements of the tidal radius of Arp 2 and Terzan 8 .
These two clusters are remarkably extended and with low concentrations ; with a concentration of only c = 0.41 \pm 0.02 , Terzan 8 is less concentrated than any cluster in our Galaxy .

Blue stragglers are identified in the four clusters , and their spatial distribution is compared to those of horizontal branch and red giant branch stars .
The blue straggler properties do not provide evidence of mass segregation in Terzan 8 , while Arp 2 probably shares the same status , although with less confidence .
In the case of NGC 5634 and Palomar 12 , blue stragglers are significantly less populous , and their analysis suggests that the two clusters have probably undergone mass segregation .