Title: The extended stellar substructures around four metal-poor globular clusters in the Galactic 
bulge

Abstract:
The spatial density distribution of stars around four metal-poor globular clusters (NGC 6266, 
NGC 6626, NGC 6642 and NGC 6723) in the Galactic bulge region was investigated in order to 
find the extended stellar substructures. We used wide-field deep J, H, and K imaging data 
obtained from the WFCAM near-infrared array on United Kingdom Infrared Telescope. We 
minimized the contamination of field stars around the clusters using statistical weighted filtering 
algorithm. We find that the two-dimensional isodensity contour maps of four clusters display 
tidal stripping stellar features beyond tidal radius, in the form of tidal tail (NGC 6266 and NGC 
6626) or small density lobes/chunk (NGC 6642 and NGC 6723). The extending directions of 
substructures are Galactic center or anticenter, and the proper motions of the clusters. The 
observed radial 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 results imply that four globular 
clusters in the Galactic bulge region have experienced strong environmental effect such as tidal 
force or bulge/disk shock of the Galaxy. 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.