We present a comprehensive study of the star cluster population and the hierarchical structure in the clustering of blue stars with ages \sim < 500 Myr in the Local Group dwarf irregular galaxy NGC 6822 .
Our observational material comprises the most complete optical stellar catalog of the galaxy from imaging with the Suprime-Cam at the 8.2-m Subaru Telescope .
We identify 47 distinct star clusters with the application of the nearest-neighbor density method to this catalog for a detection threshold of 3 \sigma above the average stellar density .
The size distribution of the detected clusters can be very well approximated by a Gaussian with a peak at \sim 68 pc .
The total stellar masses of the clusters are estimated by extrapolating the cumulative observed stellar mass function of all clusters to be in the range 10 ^ { 3 } - 10 ^ { 4 } M _ { \normalsize \odot } .
Their number distribution is fitted very well by a power-law with index \alpha \sim 1.5 \pm 0.7 , which is consistent with the cluster mass functions of other Local Group galaxies and the cluster initial mass function .

The application of the nearest-neighbor density method for various density thresholds , other than 3 \sigma , enabled the identification of stellar concentrations in various length-scales , in addition to the detected star clusters of the galaxy .
The stellar density maps constructed with this technique provide a direct proof of hierarchically structured stellar concentrations in NGC 6822 , in the sense that smaller dense stellar concentrations are located inside larger and looser ones .
We illustrate this hierarchy by the so-called dendrogram , or structure tree of the detected stellar structures , which demonstrates that most of the detected structures split up into several substructures over at least three levels .
We quantify the hierarchy of these structures with the use of the minimum spanning tree method .
We find that structures detected at 1 , 2 , and 3 \sigma density thresholds are hierarchically constructed with a fractal dimension of D \approx 1.8 .
Some of the larger stellar concentrations , particularly in the northern part of the central star-forming portion of the galaxy , coincide with IR-bright complexes previously identified with Spitzer and associated with high column density neutral gas , indicating structures that currently form stars .
The morphological hierarchy in stellar clustering , which we observe in NGC 6822 resembles that of the turbulent interstellar matter , suggesting that turbulence on pc- and kpc-scales has been probably the major agent that regulated clustered star formation in NGC 6822 .