Near-Infrared Spectroscopy of NGC 253: Starburst and Surroundings
Near-infrared longslit spectra of NGC 253 obtained with IRSPEC at the ESO NTT are presented. By analysis of the 12CO 2.29µm bandhead we find that the stellar population in the central starburst region (r ~ 150 pc) rotates more slowly than the gas, but has a velocity dispersion of 128km/s, about twice the value found for emission lines from the gas in this region. This implies an about five times higher dynamical mass than previously derived (Rieke et al. 1980), removing the need to invoke a lower mass cutoff in the starburst initial mass function. The peak of near-infrared emission is displaced from the dynamical center.