Distant compact groups from DPOSS

The groups have at least four galaxies satisfying more stringent criteria than those used by Hickson in his pioneering work in 1982: the adopted limiting surface brightness for each group is brighter (24mag/arcsec^2^ instead of 26mag/arcsec^2^), and the spread in magnitude among the member galaxies is narrower (2mag instead of 3).

We also adopt a slightly modified version of the isolation criterion used by Hickson, in order to avoid rejecting groups with projected nearby faint background galaxies. A 10% contamination rate due to projection effects is expected for this sample based on extensive simulations.