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We report high resolution imaging of the ultraluminous infrared galaxy Arp220 at 1.1, 1.6, and 2.22 microns with NICMOS on the HST. Thediffraction-limited images at 0.1--0.2 arcsecond resolution clearly resolveboth nuclei of the merging galaxy system and reveal for the first time a numberof luminous star clusters in the circumnuclear envelope. The morphologies ofboth nuclei are strongly affected by dust obscuration, even at 2.2 microns :the primary nucleus (west) presents a crescent shape, concave to the south andthe secondary (eastern) nucleus is bifurcated by a dust lane with the southerncomponent being very reddened. In the western nucleus, the morphology of the2.2 micron emission is most likely the result of obscuration by an opaque diskembedded within the nuclear star cluster. The morphology of the centralstarburst-cluster in the western nucleus is consistent with either acircumnuclear ring of star formation or a spherical cluster with the bottomhalf obscured by the embedded dust disk. Comparison of cm-wave radio continuummaps with the near-infrared images suggests that the radio nuclei lie in thedust disk on the west and near the highly reddened southern component of theeastern complex. The radio nuclei are separated by 0.98 arcseconds(corresponding to 364 pc at 77 Mpc) and the half-widths of the infrared nucleiare approximately 0.2-0.5 arcseconds. At least 8, unresolved infrared sources-- probably globular clusters -- are also seen in the circumnuclear envelope atradii 2-7 arcseconds . Their near-infrared colors do not significantlyconstrain their ages.Comment: LaTex, 15 pages with 1 gif figure and 5 postscript figures. ApJL  accepte

NICMOS Imaging of the Nuclei of Arp 220