PCG J1528+4235 B , the SIMBAD biblio

We have identified 84 small, high-density groups of galaxies out to z∼0.2 in a region of ∼2000 deg² around the north Galactic pole using the digitized Second Palomar Observatory Sky Survey. 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 (24 mag.arcsec^–2 instead of 26 mag.arcsec^–2), and the spread in magnitude among the member galaxies is narrower (2 mag 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.