HICKSONS COMPACT-GROUPS OF GALAXIES - FAR-INFRARED ENHANCEMENT

Hickson et al. have claimed that infrared emission is enhanced in compact groups of galaxies, and they have attributed the enhancement to interactions. Their conclusion is based on the comparison of the shape of the 60-mu m luminosity function of these galaxies with that of the IRAS bright galaxy sample, and their infrared emission with that from samples of isolated galaxies and cluster galaxies. Sulentic & De Mello Rabaca, on the other hand, have concluded that there is little evidence for interactive enhancement of far-infrared emission in compact groups of galaxies. They show that Hickson et al. have overestimated the quantity of far-infrared emission from the Hickson groups of galaxies. I have obtained the distributions of the galaxies for three subgroups with (i) log(L(ir)/L(op)) > 0, (ii) log(L(ir)/L(op)) < 0, and (iii) no infrared and radio emission, in terms of the tidal effect of the group as well as that of the closest pair of galaxies in the compact groups. The distributions of the three subgroups are very similar, leading to the conclusion that there is no clear evidence of tidal interaction enhancement of far-infrared emission in Hickson's compact groups of galaxies, and thus supporting the claim of Sulentic & De Mello Rabaca.