The First Metallicity Study of M83 using the integrated UV light of Star
  Clusters
  Stellar populations are powerful tools for investigating the evolution of
extragalactic environments. We present the first UV integrated-light
spectroscopic observations for 15 young star clusters in the starburst M83 with
a special focus on metallicity measurements. The data were obtained with the
Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope. We
analyse the data applying an abundance technique previously used to study an
optical set of star clusters. We estimate a central metallicity of [Z] =
$+$0.20 $\pm$ 0.15 dex in agreement with those obtained through independent
methods, i.e. $J$-band and blue supergiants. We estimate a UV metallicity
gradient of $-$0.041 $\pm$ 0.022 dex kpc$^{-1}$ consistent with the optical
metallicity gradient of $-$0.040 $\pm$ 0.032 dex kpc$^{-1}$ for $R/R_{25}<0.5$.
Combining our stellar metallicities, UV and optical, with those from HII
regions (strong-line abundances based on empirical calibrations) we identify
two possible breaks in the gradient of M83 at galactocentric distances of
$R\sim0.5$ and $1.0\:R_{25}$. If the abundance breaks are genuine, the
metallicity gradient of this galaxy follows a steep-shallow-steep trend, a
scenario predicted by three-dimensional (3D) numerical simulations of disc
galaxies. The first break is located near the corotation radius. This first
steep gradient may have originated by recent star formation episodes and a
relatively young bar ($<$1 Gyr). In the numerical simulations the shallow
gradient is created by the effects of dilution by outflow where low-metallicity
material is mixed with enriched gas. And finally, the second break and last
steep gradient mark the farthest galactocentric distances where the outward
flow has penetrated.
