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[78.03] The Stellar Populations of Nearby Early-Type Galaxies

K. D. Concannon, J. A. Rose (UNC-CH), N. Caldwell (SAO)

We have obtained high quality spectra of 120 early-type galaxies with the 1.5m telescope at the F.\ L.\ Whipple Observatory. The sample galaxies are from both the Virgo cluster and the nearby field environment and cover a large range in central velocity dispersion (50 km/s <\sigma< 300 km/s), magnitude (-16.5 B< -22.0) and morphology (E, S0, dE, dS0). With a wavelength coverage of 3500 <\lambda< 5500, a FWHM resolution of 1.8 Å, and a typical S/N of 50 or better near H\delta, the spectra are ideal for analyzing the stellar populations of the sample galaxies.

To determine the star formation histories, we use a variety of spectral indices, especially those of absorption lines in the blue, including the age-sensitive higher order Balmer lines. Our spectra show that the lower mass galaxies have a considerable range in absorption line strengths while the higher mass galaxies are relatively homogeneous. Based on the line strengths alone, we find that nearly 30% of the low mass galaxies in the sample show evidence of recent star formation, while less than 5% of the more massive galaxies do. The detailed star formation history of the sample is further analyzed with stellar population models.

The author(s) of this abstract have provided an email address for comments about the abstract: dendy@physics.unc.edu

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