Density profile. Left panel: grey points correspond to the observed density profile of the cluster NGC 1751. The contribution from field contamination is denoted by the grey dotted horizontal line. The profile in blue is obtained after subtracting the background contamination from the actual density estimate, and it is fitted with the EEF profile. Right panel: corresponding quantities in a logarithmic scale. The vertical lines indicate the core radius, the corresponding half-mass radius denoted by R_hm, and the distances indicated as R_f and R_2f. The background level (bg) is marked by a horizontal line.