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M. Geha, P. Guhathakurta (UCO/Lick Observatory), R. P. van der Marel (STScI)
We present velocity and velocity dispersion profiles for twelve dwarf elliptical (dE) galaxies in the Virgo Cluster observed with the Keck telescope and Echelle Spectrograph and Imager (ESI). In combination with previous measurements, we find that 11 of 25 Virgo dEs with resolved kinematics are roughly consistent with rotational flattening, while the remaining dEs have no detectable major axis rotation. Despite this apparent dichotomy in rotational properties, the two types of dEs are virtually identical in all available photometric properties; the only exception is that the rotating galaxies have, on average, slightly higher surface brightness. Both sets of dEs are confined to a small region of the Fundamental Plane, suggesting that they share a similar formation history. The environments of both classes of dEs appear to be diverse in terms of their proximity to larger galaxies in real or velocity space within the cluster.
Finally, we compare the Virgo Cluster dEs to five dEs in lower density galaxy group environments. These group galaxies are morphologically classified as "dE", but have higher central surface brightnesses placing them in the zone of the Fundamental Plane between other known dEs and normal low luminosity ellipticals. All of these group "dE" galaxies show significant stellar rotation; one object is kinematically peculiar with evidence of a counter-rotating core. Three of the five group "dEs" have emission lines. These data suggest that environment plays a significant role in the evolution of dE galaxies.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.