ABSORPTION-LINE GRADIENTS IN THE SPECTRUM OF M32

Long-slit spectroscopic observations, spanning the wavelength range 4000- 10 000 angstrom, are presented of the Local Group compact elliptical galaxy M32. The data are used to investigate the spatial characteristics of fifteen atomic and molecular features out to radial distances in excess of 20 arcsec from the nucleus. The significance of spectroscopic gradients are assessed using two statistical tests, and it is concluded that roughly half of the features considered in the current study systematically weaken with radius. A grid of model spectra are constructed to investigate the effects of variations in age and mass function exponent, and it is suggested that the observed gradients could be due to subtle radial variations in both mean metallicity and age, such that the nucleus of M32 contains stars which are younger and more metal-rich than those in the outer regions. The effects of combined metallicity and age gradients on the broadband radial colors of M32 are investigated, and it is predicted that whereas only mild gradients, amounting to a few hundredths of a magnitude, are predicted in U - B and B - V, a much larger gradient, on the order of a few tenths of a magnitude, should be present in V - K. These predictions are not inconsistent with the observed radial behavior of broadband colors in M32, although the scatter in these data is large. Finally, the 9900 angstrom, FeH bands are weak in the nucleus of M32, confirming previous observations of these features and suggesting that the fractional content of late M dwarfs is not markedly higher than in the solar neighborhood.