2 Micron spectroscopy of the nucleus of NGC 1068

A 2.0-2.4 μm spectrum taken at a resolution of 5 cm-1 (350 km s-1) with a small aperture (3''.8) centered on the nucleus of NGC 1068 exhibits both stellar and interstellar features. Stars are evident from the presence of first overtone CO absorption bands, the strengths of which suggest that late-type giant stars contribute about 25% of the 2.3 μm continuum within 2 '' (200 pc) of the galactic center. The estimated velocity dispersion of the stars is < or approx. =200 km s-1. Subtraction of this starlight from the spectrum leaves a gray body continuum component characterized by Tapprox.800 K. The K band flux distribution of this nonstellar emission suggests an identification with the compact source dominant at lambda> or approx. =3 μm and is inconsistent with extrapolation of the ν/sup -1.85/ power law ultraviolet source. Measured Brackett γ (n = 7→4) and quadrupole H2 emission line fluxes are in agreement with previous, larger aperture measurements, implying that both the atomic and molecular emissions are predominantly confined to within 200 pc of the nucleus. The observed H2 lines are much narrower than atomic emission lines, exhibiting widths similar to those of stellar absorption features. We argue that the H2 lines are formed in molecular clouds whose kinematics are determined by the gravitational potential of the nucleus. Comparison of infrared luminosity, B2lt. slash luminosity, total H2 line luminosity, and cloud mass supports the hypothesis that the infrared luminosity of NGC 1068 is determined by the level of star formation activity