Spectroscopy with the Keck II 10-meter 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 is presented for six Virgo Cluster dwarf elliptical ( dE ) galaxies in the absolute magnitude range -15.7 \leq { M _ { V } } \leq - 17.2 .
The mean line-of-sight velocity and velocity dispersion are resolved as a function of radius along the major axis of each galaxy , nearly doubling the total number of dEs with spatially-resolved stellar kinematics .
None of the observed objects shows evidence of strong rotation : upper limits on v _ { rot } / \sigma , the ratio of the maximum rotational velocity to the mean velocity dispersion , are well below those expected for rotationally-flattened objects .
Such limits place strong constraints on dE galaxy formation models .
Although these galaxies continue the trend of low rotation velocities observed in Local Group dEs , they are in contrast to recent observations of large rotation velocities in slightly brighter cluster dEs .
Using surface photometry from Hubble Space Telescope Based on observations with the NASA/ESA Hubble Space Telescope , obtained at the Space Telescope Science Institute , which is operated by the Association of Universities for Research in Astronomy , Inc. , under NASA contract NAS 5-26555 . Wide Field Planetary Camera 2 images and spherically-symmetric dynamical models , we determine global mass-to-light ratios 3 \leq \Upsilon _ { V } \leq 6 .
These ratios are comparable to those expected for an old to intermediate-age stellar population and are broadly consistent with the observed ( V - I ) colors of the galaxies .
These dE galaxies therefore do not require a significant dark matter component inside an effective radius .
We are able to rule out central black holes more massive than \sim 10 ^ { 7 } \mbox { $M _ { \odot } $ } .
For the five nucleated dEs in our sample , kinematic and photometric properties were determined for the central nucleus separately from the underlying host dE galaxy .
These nuclei are as bright or brighter than the most luminous Galactic globular clusters and lie near the region of Fundamental Plane space occupied by globular clusters .
In this space , the Virgo dE galaxies lie in the same general region as Local Group and other nearby dEs , although non-rotating dEs appear to have a slightly higher mean mass and mass-to-light ratio than rotating dEs ; the dE galaxies occupy a plane parallel to , but offset from , that occupied by normal elliptical galaxies .