NICMOS IMAGING OF THE NUCLEI OF ARP-220

We report high-resolution imaging of the ultraluminous infrared galaxy Arp 220 at 1.1, 1.6, and 2.22 mu m with the Near-Infrared Camera and Multiobject Spectrometer on the Hubble Space Telescope. The diffractio n-limited images at 0''.1-0''.2 resolution clearly resolve both nuclei of the merging galaxy system and reveal for the first time a number o f luminous star clusters in the circumnuclear envelope. The morphologi es of both nuclei are strongly affected by dust obscuration, even at 2 .2 mu m: the primary nucleus (west) presents a crescent shape, concave to the south, and the secondary (eastern) nucleus is bifurcated by a dust lane with the southern component being very reddened. In the west ern nucleus, the morphology of the 2.2 mu m emission is most likely th e result of obscuration by an opaque disk embedded in the nuclear star cluster. The morphology of the central starburst cluster in the weste rn nucleus is consistent with either a circumnuclear ring of star form ation or a spherical cluster with the bottom half obscured by the embe dded dust disk. Comparison of centimeter-wave radio continuum maps wit h the near-infrared images suggests that the radio nuclei lie in the d ust disk on the west and near the highly reddened southern component o f the eastern complex. The radio nuclei are separated by 0''.98 (corre sponding to 364 pc at 77 Mpc), and the half-widths of the infrared nuc lei are similar to 0''.2-0''.5. At least eight unresolved infrared sou rces--probably globular clusters--are also seen in the circumnuclear e nvelope at radii of 2''-7''. Their near-infrared colors do not signifi cantly constrain their ages.