A wide-field photometric survey for extratidal tails around five
  metal-poor globular clusters in the Galactic halo
  Wide-field deep gri images obtained with the Megacam of the
Canada-France-Hawaii Telescope (CFHT) are used to investigate the spatial
configuration of stars around five metal-poor globular cluster M15, M30, M53,
NGC 5053, and NGC 5466, in a field-of-view ~3 degree. Applying a mask filtering
algorithm to the color-magnitude diagrams of the observed stars, we sorted
cluster's member star candidates that are used to examine the characteristics
of the spatial stellar distribution surrounding the target clusters. The
smoothed surface density maps and the overlaid isodensity contours indicate
that all of the five metal-poor globular clusters exhibit strong evidence of
extratidal overdensity features over their tidal radii, in the form of extended
tidal tails around the clusters. The orientations of the observed extratidal
features show signatures of tidal tails tracing the clusters' orbits, inferred
from their proper motions, and effects of dynamical interactions with the
Galaxy. Our findings include detections of a tidal bridge-like feature and an
envelope structure around the pair of globular clusters M53 and NGC 5053. The
observed radial surface density profiles of target clusters have a deviation
from theoretical King models, for which the profiles show a break at
0.5~0.7r_t, extending the overdensity features out to 1.5~2r_t. Both radial
surface density profiles for different angular sections and azimuthal number
density profiles confirm the overdensity features of tidal tails around the
five metal-poor globular clusters. Our results add further observational
evidence that the observed metal-poor halo globular clusters originate from an
accreted satellite system, indicative of the merging scenario of the formation
of the Galactic halo.
