Object name: ARP173
Arp 173/UGC 9561 is a pair of galaxies about 410 million light-years away in the southeastern corner of Bootes. The northern galaxy is MCG +02-38-20/PGC 53053 while the southern is MCG +02-38-19/PGC 53054. The northern one is classed S0 by NED which I find puzzling as it seems to have too much structure for that classification. The southern one is classed simply as S? Except for the plume, it seems to fit the S0 class. Makes me wonder if NED reversed these classifications. The PGC designations also appear reversed as normally they are in RA order but that is not the case with these two. In any case, Arp put this in his class for galaxies with narrow counter tails. There is certainly a nice narrow plume heading south and a bit west from the southern galaxy. There appears to be a broad plume toward the northern galaxy as well. Several plumes extend in various directions from the northern galaxy. Obviously, these had a close passage by each other in the recent past. One paper indicates the authors think the northern galaxy should be designated as a Seyfert 2 galaxy. NED apparently disagrees as they don't indicate this in their classification.