Title: Chemical abundances of two extragalactic young massive clusters,
Abstract: We use integrated-light spectroscopic observations to measure metallicities
and chemical abundances for two extragalactic young massive star clusters
(NGC1313-379 and NGC1705-1). The spectra were obtained with the X-Shooter
spectrograph on the ESO Very Large Telescope. We compute synthetic
integrated-light spectra, based on colour-magnitude diagrams for the brightest
stars in the clusters from Hubble Space Telescope photometry and theoretical
isochrones. Furthermore, we test the uncertainties arising from the use of
Colour Magnitude Diagram (CMD) +Isochrone method compared to an Isochrone-Only
method. The abundances of the model spectra are iteratively adjusted until the
best fit to the observations is obtained. In this work we mainly focus on the
optical part of the spectra. We find metallicities of [Fe/H] = $-$0.84 $\pm$
0.07 and [Fe/H] = $-$0.78 $\pm$ 0.10 for NGC1313-379 and NGC1705-1,
respectively. We measure [$\alpha$/Fe]=$+$0.06 $\pm$ 0.11 for NGC1313-379 and a
super-solar [$\alpha$/Fe]=$+$0.32 $\pm$ 0.12 for NGC1705-1. The roughly solar
[$\alpha$/Fe] ratio in NGC1313-379 resembles those for young stellar
populations in the Milky Way (MW) and the Magellanic Clouds, whereas the
enhanced [$\alpha$/Fe] ratio in NGC1705-1 is similar to that found for the
cluster NGC1569-B by previous studies. Such super-solar [$\alpha$/Fe] ratios
are also predicted by chemical evolution models that incorporate the bursty
star formation histories of these dwarf galaxies. Furthermore, our
$\alpha$-element abundances agree with abundance measurements from H II regions
in both galaxies. In general we derive Fe-peak abundances similar to those
observed in the MW and Large Magellanic Cloud (LMC) for both young massive
clusters. For these elements, however, we recommend higher-resolution
observations to improve the Fe-peak abundance measurements.