Bibcode
DOI
Beasley, Michael A.; Strader, Jay; Brodie, Jean P.; Cenarro, A. Javier; Geha, M.
Bibliographical reference
The Astronomical Journal, Volume 131, Issue 2, pp. 814-827.
Advertised on:
2
2006
Citations
37
Refereed citations
33
Description
We present an analysis of the globular cluster (GC) system of the
nucleated dwarf elliptical galaxy VCC 1087 in the Virgo Cluster based on
Keck LRIS spectroscopy and archival Hubble Space Telescope Advanced
Camera for Surveys imaging. We estimate that VCC 1087 hosts a total
population of 77+/-19 GCs, which corresponds to a relatively high V-band
specific frequency of 5.8+/-1.4. The g475-z850
color distribution of the GCs shows a blue (metal-poor) peak with a tail
of redder (metal-rich) clusters similar in color to those seen in
luminous elliptical galaxies. The luminosity function of the GCs is
lognormal and peaks at
MTOg475=-7.2+/-0.3,
MTOz850=-8.1+/-0.2. These peak
positions are consistent with those found for luminous Virgo elliptical
galaxies, suggesting either the lack of or, surprisingly similarly, the
dynamical destruction processes of GCs among dwarf and giant galaxies.
Spectroscopy of a subsample of 12 GCs suggests that the GC system is old
and coeval (>~10 Gyr), with a fairly broad metallicity distribution
(-1.8<~[M/H]<~-0.8). In contrast, an integrated spectrum of the
underlying galaxy starlight reveals that its optical luminosity is
dominated by metal-rich, intermediate-age stars. The radial velocities
of the GCs suggest rotation close to the major axis of the galaxy, and
this rotation is dynamically significant with
(vrot/σlos)*>1. A compilation
of the kinematics of the GC systems of nine early-type galaxies shows
surprising diversity in the (vrot/σlos)
parameter for GC systems. In this context, the GC system of VCC 1087
exhibits the most significant rotation-to-velocity dispersion signature.
Dynamical mass modeling of the velocity dispersion profile of the GCs
and galaxy stars suggests fairly constant mass-to-light ratios of ~3 out
to 6.5 kpc. The present observations can entertain both baryonic and
nonbaryonic solutions, and GC velocities at larger radii would be most
valuable with regard to this issue. Finally, we discuss the evolution of
VCC 1087 in terms of the galaxy ``harassment'' scenario and conclude
that this galaxy may well be the remains of a faded, tidally perturbed
Sc spiral.
Some of the 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.