Rotation (?) in 13 elliptical galaxies.

Rotation data are presented for 13 elliptical galaxies, and compared with the oblate models of Gott (1975), Larson (1975), and Wilson (1975). It is found that, on average, most elliptical galaxies have one-third the peak rotational velocity required by these models, with an estimated upper limit of two-thirds the expected rotation. This result is independent of the distance scale. Oblate models in which the flattening is a result of rotation appear to be precluded by these data. Plausible alternatives appear to be that ellipticals are (1) triaxial ellipsoids (or oblate spheroids) in which the flattening is due to remnant anisotropy in the velocity distribution, as suggested by Binney (1978), or (2) rotating prolate ellipsoids, as suggested by Miller (1978). Curiously, one giant elliptical rotates as expected.