THE SURFACE DENSITY PROFILES AND LENSING CHARACTERISTICS OF HICKSON COMPACT GROUPS OF GALAXIES

摘要

A statistical method is developed to infer the typical density profiles of poor galaxy systems without resort to binning of data or assuming a given center to each system. The method is applied to the accordant redshift quartets in Hickson compact groups (HCGs). The distribution of separations in these groups is consistent with a unique generalized and modified Hubble surface density profile, with best-fit asymptotic slope β = 1.4 and core radius R_c = 18 h~(-1) kpc, although a King profile (β = 1) is also consistent with the data (with R_c = 6 h~(-1) kpc). These distributions are more concentrated than what has been determined previously for these groups. HCGs are unlikely to act as strong gravitational lenses, but analogous systems 5-10 times more distant should produce a nonnegligible fraction of giant arcs.