UV Spectra, Line Indices of M31 Globular Clusters and E Galaxy Cores

Abstract

Observations in integrated light (2200-4800 A, 8 to 11 A resolution, S/N > 20) of 4 M31 globular clusters and of the cores of six gE galaxies made with the HST/FOS are presented and analyzed. These data are supplemented by IUE observations of M32, Galactic globulars and stars. From these data we measure UV colors and absorption line strength (ALS) indices, including the key NH feature at 3360 A. We find that our data divide the M31 globular clusters, Galactic globular clusters/Galactic stars, and gE galaxies into three different stellar populations. The old stellar populations of M31 globular clusters and elliptical galaxies are more similar to each other than each is to the Galactic stellar population. Of special note is that the NH feature is so strong in the spectra of M31 globulars that a large (>20) overabundance in nitrogen in these stars, relative to that in Galactic stars, is likely required. Other ALS indices (of Mg, Al) also show significant differences.