THE RADIO-EMISSION FROM THE ULTRALUMINOUS FAR-INFRARED GALAXY NGC-6240

We present new radio observations of the ''prototypical'' ultraluminou s far-infrared galaxy NGC 6240, obtained using the VLA at lambda = 20 cm in B-configuration and at lambda = 3.6 cm in A-configuration. These data, along with those from four previous VLA observations, are used to perform a comprehensive study of the radio emission from NGC 6240. Approximately 70% (similar to 3 X 10(23) W Hz(-1)) of the total radio power at 20 cm originates from the nuclear region (less than or simila r to 1.5 kpc), of which half is emitted by two unresolved (R less than or similar to 36 pc) cores and half by a diffuse component. The radio spectrum of the nuclear emission is relatively flat (alpha approximat e to 0.6; S-nu) proportional to nu(-alpha). The supernova rate require d to power the diffuse component is consistent with that predicted by the stellar evolution models of Rieke et al. (1985). If the radio emis sion from the two compact cores is powered by supernova remnants, then either the remnants overlap and form hot bubbles in the cores, or the y are very young (less than or similar to 100 yr). Nearly all of the r emaining 30% of the total radio power comes from an ''armlike'' region extending westward from the nuclear region. The western arm emission has a steep spectrum (alpha approximate to 1.0), suggestive of aging e ffects from synchrotron or inverse-Compton losses, and is not correlat ed with starlight; we suggest that it is synchrotron emission from a s hell of material driven by a galactic superwind. Inverse Compton scatt ering of far-infrared photons in the radio sources is expected to prod uce an X-ray flux of similar to 2- 6 x 10(-14) ergs s(-1) cm(-2) in th e 2-10 keV band. No significant radio emission is detected from or nea r the possible ultramassive ''dark core'' hypothesized by Bland-Hawtho rn, Wilson, & Tully (1991).