Detailed abundances from integrated-light spectroscopy: Milky Way
  globular clusters
  We test the performance of our analysis technique for integrated-light
spectra by applying it to seven well-studied Galactic GCs that span a wide
range of metallicities. Integrated-light spectra were obtained by scanning the
slit of the UVES spectrograph on the ESO Very Large Telescope across the
half-light diameters of the clusters. We modelled the spectra using resolved
HST colour-magnitude diagrams (CMDs), as well as theoretical isochrones, in
combination with standard stellar atmosphere and spectral synthesis codes. The
abundances of Fe, Na, Mg, Ca, Ti, Cr, and Ba were compared with literature data
for individual stars in the clusters. The typical differences between iron
abundances derived from our integrated-light spectra and those compiled from
the literature are less than 0.1 dex. A larger difference is found for one
cluster (NGC 6752), and is most likely caused primarily by stochastic
fluctuations in the numbers of bright red giants within the scanned area. As
expected, the alpha-elements (Ca, Ti) are enhanced by about 0.3 dex compared to
the Solar-scaled composition, while the [Cr/Fe] ratios are close to Solar. When
using up-to-date line lists, our [Mg/Fe] ratios also agree well with literature
data. Our [Na/Fe] ratios are, on average, 0.08-0.14 dex lower than average
values quoted in the literature, and our [Ba/Fe] ratios may be overestimated by
0.20-0.35 dex at the lowest metallicities. We find that analyses based on
theoretical isochrones give very similar results to those based on resolved
CMDs. Overall, the agreement between our integrated-light abundance
measurements and the literature data is satisfactory. Refinements of the
modelling procedure, such as corrections for stellar evolutionary and non-LTE
effects, might further reduce some of the remaining offsets.
