We have used a combination of multiband high-resolution and wide-field ground-based observations to image the Galactic globular cluster M75 ( NGCÂ 6864 ) .
The extensive photometric sample covers the entire cluster extension , from the very central regions out to the tidal radius , allowing us to determine the center of gravity and to construct the most extended star density profile ever published for this cluster .
We also present the first detailed star counts in the very inner regions .
The star density profile is well re-produced by a standard King model with core radius r _ { c } \sim 5.4 ^ { \prime \prime } and intermediate-high concentration c \sim 1.75 .
The present paper presents a detailed study of the BSS population and its radial distribution .
A total number of 62 bright BSSs ( with m _ { F 255 W } \lesssim 21 , corresponding to m _ { F 555 W } \lesssim 20 ) has been identified , and they have been found to be highly segregated in the cluster core .
No significant upturn in the BSS frequency has been observed in the outskirts of M75 , in contrast to several other clusters studied with the same technique .
This observational fact is quite similar to what has been found in M79 ( NGCÂ 1904 ) by ( 23 ) .
Indeed the BSS radial distributions in the two clusters is qualitatively very similar , even if in M75 the relative BSS frequency seems to decrease significantly faster than in M79 : indeed it decreases by a factor of 5 ( from 3.4 to 0.7 ) within 1 r _ { c } .
Such evidence indicate that the vast majority of the cluster heavy stars ( binaries ) have already sunk to the core .