LONG-SLIT SPECTROSCOPY OF NEAR-ULTRAVIOLET NH ABSORPTION IN THE NUCLEI OF M31 AND M32

Using the Canada-France-Hawaii Telescope (CFHT) we have obtained long-slit near-ultraviolet spectra of the central regions of M31 and M32. The Δυ = 0 NH absorption bands near 3360 Å are detected out to distances of ∼32 arcsec in M31 and ∼15 arcsec in M32, and we have studied the spatial behavior of these features in each galaxy. NH absorption in M31 appears to vary in a complicated manner with respect to radial distance from the galaxy center, and there is no evidence for a systematic gradient. Moreover, the variations in NH strength appear to be more-or-less symmetric on a north/south axis about the central nucleus of M31. As for M32, NH absorption becomes progressively stronger with increasing distance from the center of this galaxy. Various explanations for the radial behavior of NH absorption in each galaxy are considered; these results may reflect changes in the relative contributions of early-type stars to the near-ultraviolet light output, or a radial variation in [N/Fe].