  We investigate the spatial density configuration of stars around four
metal-poor globular clusters (NGC 6266, NGC 6626, NGC 6642 and NGC 6723) in the
Galactic bulge region using wide-field deep J, H, and K imaging data obtained
with the WFCAM near-infrared array on United Kingdom Infrared Telescope.
Statistical weighted filtering algorithm for the stars on the color-magnitude
diagram is applied in order to sort cluster member candidates from the field
star contamination. In two-dimensional isodensity contour maps of the clusters,
we find that all of the four globular clusters exhibit strong evidence of
tidally stripping stellar features beyond tidal radius, in the form of tidal
tail or small density lobes or chunk. The orientations of the extended stellar
substructures are likely to be associated with the effect of the dynamic
interaction with the Galaxy and the cluster space motion. The observed radial
density profiles of the four globular clusters also describe the extended
substructures; they depart from theoretical King and Wilson models and have an
overdensity feature with a break in a slope of profile at the outer region of
clusters. The observed results could imply that four globular clusters in the
Galactic bulge region have experienced strong environmental effect such as
tidal force or bulge or disk shock of the Galaxy in the dynamical evolution of
the globular clusters. These observational results provide us further
constraints to understand the evolution of clusters in the Galactic bulge
region as well as the formation of the Galaxy.
