We present a study on four new star clusters discovered in the halo of the intriguing dwarf irregular galaxy NGC 6822 from a wide field survey covering 3 \arcdeg \times 3 \arcdeg area carried out with MegaCam at Canada-France-Hawaii Telescope ( CFHT ) .
The star clusters have extended structures with half-light radii { R } _ { h } \approx 7.5 – 14.0 pc , larger than typical Galactic globular clusters and other known globular clusters in NGC 6822 .
The integrated colors and color magnitude diagrams ( CMD ) of resolved stars suggest that the new star clusters are 2 – 10 Gyr old and relatively metal poor with Z=0.0001–0.004 based on the comparison with theoretical models .
The projected distance of each star cluster from the galaxy center ranges from 10.7 \arcmin ( \approx 1.5 kpc ) to 77 \arcmin ( \approx 11 kpc ) , far beyond the optical body of the galaxy .
Interestingly , the new star clusters are aligned along the elongated old stellar halo of NGC 6822 , which is almost perpendicular to the HI gas distribution where young stellar populations exist .
We also find that the colors and half-light radii of the new clusters are correlated with the galactocentric distance : clusters farther from the galaxy center are larger and bluer than those closer to the galaxy center .
We discuss the stellar structure and evolution of NGC 6822 implied by these new extended star clusters in the halo .
We also discuss the current status of observational and theoretical understandings regarding the origin of extended star clusters in NGC 6822 and other galaxies .