CHEMODYNAMICS OF COMPACT STELLAR SYSTEMS IN NGC 5128: HOW SIMILAR ARE GLOBULAR CLUSTERS, ULTRA-COMPACT DWARFS, AND DWARF GALAXIES?
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abstract
Velocity dispersion measurements are presented for luminous GCs in NGC 5128
derived from high-res. UVES spectra. The measurements are made with the pPXF
code that parametrically recovers line-of-sight velocity dispersions. Combining
the measured velocity dispersions with surface photometry and structural
parameter data from HST enables both dynamical masses and M/L ratios to be
derived. The fundamental plane relations of these clusters are investigated in
order to fill the apparent gap between the relations of Local Group GCs and
more massive early-type galaxies. It is found that the properties of these
massive stellar systems match those of nuclear clusters in dwarf elliptical
galaxies and UCDs better than those of Local Group GCs, and that all objects
share similarly old (>8 Gyr) ages, suggesting a possible link between the
formation and evolution of dE,Ns, UCDs and massive GCs. We find a very steep
correlation between dynamical (M/L) ratio and dynamical mass of the form
(M/L)_dyn ~ M_dyn^(0.24+/-0.02) above M_dyn = 2x10^6 Msol. Formation scenarios
are investigated with a chemical abundance analysis using absorption line
strengths calibrated to the Lick/IDS index system. The results lend support to
two scenarios contained within a single general formation scheme. Old, massive,
super-solar [alpha/Fe] systems are formed on short (<100 Myr) timescales
through the merging of single-collapse GCs which themselves are formed within
single, giant molecular clouds. More intermediate- and old-aged (~3-10 Gyr),
solar- to sub-solar [alpha/Fe] systems are formed on much longer (~Gyr)
timescales through the stripping of dE,Ns in the 10^13-10^15 Msol potential
wells of massive galaxies and galaxy clusters.
