Stellar dynamics observations of a double nucleus in M 83

We report on the discovery of a double nucleus in M83, based on measurement s of the line of sight Velocity distribution of stars observed at near infr ared wavelengths with the VLT ISAAC spectrograph. We observe two peaks sepa rated by 2."7 in the velocity dispersion profile of light from late-type st ars measured along a slit 0."6 wide, centered on the peak of K band emissio n and with P.A. 51.7 degrees. The first peak coincides with the peak of the K band light distribution, widely assumed to be the galaxy nucleus. The se cond peak, of almost equal strength, almost coincides with the center of sy mmetry of the outer isophotes of the galaxy. The secondary peak location ha s little K band emission, and appears to be significantly extincted, even a t near infrared wavelengths. It also lies along a mid-infrared bar, previou sly identified by Gallais et al. (1991) and shows strong hydrogen recombina tion emission at 1.875 mum. If we interpret the observed stellar velocity d ispersion as coming from a virialized system, the two nuclei would each con tain an enclosed mass of 13.2 x 10(6) M. within a radius of 5.4 pc. These c ould either be massive star clusters, or supermassive dark objects.