ABSTRACT. Images of Arp 220 from 3.45 to 24.5 μm with 05 resolution are presented that clearly separate the nucleus into at least two components. The western component is about 3 times more luminous than the eastern component, but the silicate absorption in the fainter, eastern component is roughly 50% greater than the absorption in the western component. Each component is marginally resolved. The two components seen at 24.5 μm are identified with the two radio components. The western source most likely coincides with the high-extinction disk previously suggested to exist in Arp 220, while the eastern nucleus is identified with a faint, highly reddened source seen in HST 2.2 μm NICMOS images. The two nuclei together account for essentially all of the measured 24.5 μm flux density. Two models are presented, both of which fit the observations. In one the majority of the total luminosity is produced in an extended star formation region, and in the other most of the luminosity is produced in the compact but extincted regions associated with the two nuclei seen at 24.5 μm. In both pictures, substantial luminosity at 100 μm emerges from a component having a diameter of 2''-3'' (~1 kpc).

Subject headings: galaxies: individual (Arp 220); galaxies: nuclei; galaxies: structure; infrared: galaxies

^* Based in part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology and the University of California.

Print publication: Issue 1 (1999 March 1)
Received 1998 July 27, accepted for publication 1998 October 6