The Surface Density Profiles and Lensing Characteristics of Hickson Compact Groups of Galaxies

A statistical method is developed to infer the typical density profiles ofpoor galaxy systems without resort to binning of data or assuming a givencenter to each system. The method is applied to the accordant redshift quartetsin Hickson's compact groups (HCGs). The distribution of separations in thesegroups is consistent with a unique generalized modified Hubble surface densityprofile, with best-fit asymptotic slope beta = 1.4 and core radius R_c = 18h^{-1} kpc, although a King profile (beta = 1) is also consistent with the data(with R_c = 6 h^{-1} kpc). These distributions are more concentrated than whathas been previously determined for these groups. HCGs are unlikely to act asstrong gravitational lenses, but analogous systems 5 to 10 times more distantshould produce a non-negligible fraction of giant arcs.Comment: ApJL in press. 12 pages, incl. 1 table and 2 figures. LaTeX, uses aaspp