We present spatially-resolved internal kinematics and stellar chemical abundances for a sample of dwarf elliptical ( dE ) galaxies in the Virgo Cluster observed with the Keck telescope Data presented herein were obtained at the W. M. Keck Observatory , which is operated as a scientific partnership among the California Institute of Technology , the University of California and the National Aeronautics and Space Administration .
The Observatory was made possible by the generous financial support of the W. M. Keck Foundation . and Echelle Spectrograph and Imager .
In combination with previous measurements , we find that 4 out of 17 dEs have major axis rotation velocities consistent with rotational flattening , while the remaining dEs have no detectable major axis rotation .
Despite this difference in internal kinematics , rotating and non-rotating dEs are remarkably similar in terms of their position in the Fundamental Plane , morphological details , stellar populations , and local environment .
We present evidence for ( or confirm the presence of ) faint underlying disks and/or weak substructure in a fraction of both rotating and non-rotating dEs , but a comparable number of counter-examples exist for both types which show no evidence of such structure .
Absorption-line strengths were determined based on the Lick/IDS system ( H \beta , Mgb , Fe5270 , Fe5335 ) for the central region of each galaxy .
We find no difference in the line-strength indices , and hence stellar populations , between rotating and non-rotating dE galaxies .
The best-fitting mean age and metallicity for our 17 dE sample are 5 Gyr and [ Fe / H ] = -0.3 dex , respectively , with rms spreads of 3 Gyr and 0.1 dex .
The majority of dEs are consistent with solar [ \alpha / Fe ] abundance ratios .
By contrast , the stellar populations of classical elliptical galaxies are , on average , older , more metal rich , and \alpha -enhanced relative to our dE sample .
The line-strengths of our dEs are consistent with the extrapolation of the line-strength versus velocity dispersion trend seen in classical elliptical galaxies .
Finally , the local environments of both rotating and non-rotating dEs appear to be diverse in terms of their proximity to larger galaxies in real or velocity space within the Virgo Cluster .
Thus , rotating and non-rotating dEs are remarkably similar in terms of their structure , stellar content , and local environments , presenting a significant challenge to theoretical models of their formation .