We present the largest publicly available catalogue of compact groups of galaxies identified using the original selection criteria of Hickson , selected from the Sixth Data Release ( DR6 ) of the Sloan Digital Sky Survey ( SDSS ) .
We identify 2297 compact groups down to a limiting magnitude of r = 18 ( \sim 0.24 groups degree ^ { -2 } ) , and 74791 compact groups down to a limiting magnitude of r = 21 ( \sim 6.7 groups degree ^ { -2 } ) .
This represents 0.9 \% of all galaxies in the SDSS DR6 at these magnitude levels .
Contamination due to gross photometric errors has been removed from the bright sample of groups , and we estimate it is present in the large sample at the 14 \% level .
Spectroscopic information is available for 4131 galaxies in the bright catalogue ( 43 % completeness ) , and we find that the median redshift of these groups is { z _ { med } } = 0.09 .
The median line-of-sight velocity dispersion within the compact groups from the bright catalogue is \sigma _ { LOS } \simeq 230 km s ^ { -1 } and their typical inter-galactic separations are of order 50 - 100 kpc .
We show that the fraction of groups with interloping galaxies identified as members is in good agreement with the predictions from our previous study of a mock galaxy catalogue , and we demonstrate how to select compact groups such that the interloper fraction is well defined and minimized .
This observational dataset is ideal for large statistical studies of compact groups , the role of environment on galaxy evolution , and the effect of galaxy interactions in determining galaxy morphology .