2019ApJ...872..116H

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 on board the Hubble Space Telescope. We analyze the data by applying an abundance technique that has previously been used to study an optical set of star clusters. We estimate a central metallicity of [Z] = +0.20 ± 0.15 dex, in agreement with estimates obtained through independent methods, i.e., J band and blue supergiants. We estimate a UV metallicity gradient of -0.041 ± 0.022 dex kpc^–1, which is consistent with the optical metallicity gradient of -0.040 ± 0.032 dex kpc^–1 for R/R₂₅< 0.5. Combining our stellar metallicities, UV and optical, with those from H II regions (strong-line abundances based on empirical calibrations), we identify two possible breaks in the gradient of M83 at galactocentric distances of R ∼ 0.5 and 1.0 R₂₅. If the abundance breaks are genuine, the metallicity gradient of this galaxy follows a steep-shallow-steep trend, a scenario predicted by three-dimensional numerical simulations of disk galaxies. The first break is located near the corotation radius. This first steep gradient may have originated in 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. Finally, the second break and last steep gradient mark the farthest galactocentric distances where the outward flow has penetrated.