2001A&A...373..836L

We show how the ratio of the abundances of Ar, Si and Fe as derived from FUSE absorption spectra of I Zw 18 are affected by large-scale stochastic velocity fields (mesoturbulence). 21-cm observations with high spatial resolution show the presence of velocity fields with large correlation lengths. FUSE observations were performed with a large entrance aperture which fully covered the galaxy. This means that the observed profiles are averaged over the full body of I Zw 18. Taking this into account, we show that the observations are consistent with the abundance ratios [α-chain/Fe] being similar to those derived from Galactic metal-poor stars. Using a mesoturbulent approach, we found that the observed profiles can be reproduced well with [Fe/H]=-2.4±0.1, and [Si, Ar/Fe]=0.7±0.1.