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J. L. Hinz, H. W. Rix (U. Arizona), G. Bernstein (U. Michigan)
We present a study of the ``Tully-Fisher relation" (TFR) in 20 Coma galaxies, based on stellar kinematics derived from stellar absorption line spectroscopy. We are following up a recent study of 18 nearby S0 galaxies (Neistein et. al., 1998) in which a large scatter (0.7 magnitudes) in the relation between I-band magnitude and circular velocity was reported, implying that no tight TFR holds for these field S0 galaxies. This conflicts with the idea that S0s are former spiral galaxies whose star-formation history was truncated by some outside mechanism. Instead, it may suggest that S0s are more closely related to elliptical galaxies. Our analysis of S0s in the Coma cluster has several advantages over the previous test: the data are independent of distance estimate errors and should not reflect any differences in the environment in which the galaxies were formed. Also, the sample of galaxies is larger and higher signal-to-noise measurements were obtained. The results should shed some light on the heterogeneous nature of S0 galaxies.