Discordant Arguments on Compact Groups

Much print has been dedicated to explaining discordant redshifts in compact groups as unrelated background galaxies. But no one has analyzed the accordant galaxies. It is shown here that when there is a brightest galaxy in the group, the remainder with differences of less than 1000 km s-1 are systematically redshifted. This is the same result as obtained in all other well-defined groups and demonstrates again an increasing intrinsic redshift with fainter luminosity. Defining discordant redshifts as 1000 km s-1 or greater than the brightest galaxy, it is shown that 76 out of 345, or 22% are discordant, reaching excesses of up to 23,000 km s-1. This large percentage cannot be explained by background contamination because the number of discordances would be expected to increase rapidly with larger excesses, exactly opposite to what is observed in compact groups. Hickson's logarithmic intensity image of the NGC 1199 group confirms earlier direct evidence from Arp that a peculiar, compact object of 13,300 km s-1 redshift is silhouetted in front of the 2705 km s-1 central galaxy.