Structural parameters for globular clusters in NGC 5128 - III. ACS surface brightness profiles and model fits
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abstract
We present internal surface-brightness profiles, based on HST/ACS imaging in
the F606W bandpass, for 131 globular cluster (GC) candidates with luminosities
10^4 - 3 x 10^6 solar, in the giant elliptical galaxy NGC 5128. Several
structural models are fit to the profile of each cluster and combined with
mass-to-light ratios from population-synthesis models, to derive a catalogue of
fundamental structural and dynamical parameters parallel in form to the
catalogues recently produced by McLaughlin & van der Marel and Barmby et al.
for GCs and massive young star clusters in Local Group galaxies. As part of
this, we provide corrected and extended parameter estimates for another 18
clusters in NGC 5128, which we observed previously. We show that, like GCs in
the Milky Way and some of its satellites, the majority of globulars in NGC 5128
are well fit by isotropic Wilson models, which have intrinsically more
distended envelope structures than the standard King lowered isothermal
spheres. We use our models to predict internal velocity dispersions for every
cluster in our sample. These predictions agree well in general with the
observed dispersions in a small number of clusters for which spectroscopic data
are available. In a subsequent paper, we use these results to investigate
scaling relations for GCs in NGC 5128.
