Dual emission-line clouds in the nuclei of the interacting pair Arp 90

During a detailed study of the interacting pair Arp 90 (= NGC 5929 + NGC 5930), dual emission-line clouds were detected in the nucleus of NGC 5930(Sb) and of NGC 5929. This discovery is important because (1) dual emission-line clouds are observed in both nuclei of the interacting pair, (2) they are quite similar in their spatial, kinematical, and radio properties but quite different in the excitation levels of their ionized gas, and (3) NGC 5930 is identified as the IRAS source 15243 + 4150 with an infrared luminosity of 20 billion solar, while NGC 5929 is not. These findings may represent a unique opportunity to clarify the relationship between Seyfert 2 nuclei and starburst or H II region type nuclei. 48 references