Low-Luminosity Early-Type Galaxies in the Coma Cluster: Variations in Spectral Properties

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Abstract
We present spectra of nine low-luminosity early-type galaxies (MB > -17.5) in the Coma Cluster. The spectra, which were obtained with the Multiple Mirror Telescope and cover the spectral region 3300–5350 Å, exhibit a large variation in Balmer line strengths. In fact, the line-strength variation among the Coma low-luminosity galaxies is as large as that found among a sample of low-luminosity elliptical galaxies in the Virgo Cluster and lower density environments. When compared with detailed population synthesis models, the variation in Balmer line strengths among the Coma galaxies indicates a range in luminosity-weighted mean age from ~1 to ~12 Gyr. The two youngest galaxies are shown to be in a poststarburst state, i.e., they are not simply former spirals whose star formation was recently terminated. Moreover, the ~1 Gyr ages of these two youngest low-luminosity galaxies are similar to those of the brighter poststarburst galaxies in the Coma Cluster.
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