2 micron spectroscopy of the nucleus of NGC 1068

Abstract

Both stellar and interstellar features are found in a 2.0-2.4 micron spectrum centered on the nucleus of NGC 1068. The strengths of first-overtone CO absorption bands suggest that late-type giant stars contribute about 25% of the 2.3 micron continuum within 200 pc of the galactic center. Subtraction of this starlight from the spectrum leaves a gray body continuum component characterized by temperatures of about 800 K. The K-band flux distribution of this nonstellar emission suggests an identification with the compact source dominant at wavelengths greater than about 3.0 microns and is consistent with extrapolation of the nu to the -1.85 power law ultraviolet source. Comparisons of IR and B gamma luminosities, total H2 line luminosity, and cloud mass in the NGC 1068 nucleus and the Orion Molecular Cloud support the hypothesis that, as in Orion, the NGC 1068 IR luminosity is determined by star formation activity but at much higher conversion efficiencies.