A Survey of Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope Sight Lines Through High-Velocity Cloud Complex C
Using archival Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope (HST) data, we have assembled a survey of eight sight lines through high-velocity cloud Complex C. Abundances of the observed ion species vary significantly for these sight lines, indicating that Complex C is not well characterized by a single metallicity. Reliable metallicities based on [O I/H I] range from 0.1 to 0.25 Z⊙. Metallicities based on [S II/H I] range from 0.1 to 0.6 Z⊙, but the trend of decreasing abundance with H I column density indicates that photoionization corrections may affect the conversion to [S/H]. We present models of the dependence of the ionization correction on H I column density; these ionization corrections are significant when converting ion abundances to elemental abundances for S, Si, and Fe. The measured abundances in this survey indicate that parts of the cloud have a higher metallicity than previously thought and that Complex C may represent a mixture of " Galactic fountain " gas with infalling low-metallicity gas. We find that [S/O] and [Si/O] have a solar ratio, suggesting little dust depletion. Further, the measured abundances suggest an overabundance of O, S, and Si relative to N and Fe. The enhancement of these α-elements suggests that the bulk of the metals in Complex C were produced by Type II supernovae and then removed from the starforming region, possibly via supernova-driven winds or tidal stripping, before the ISM could be enriched by N and Fe.
Collins, Joseph A.; Shull, J. Michael; and Giroux, Mark L.. 2003. A Survey of Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope Sight Lines Through High-Velocity Cloud Complex C. Astrophysical Journal. Vol.585(1 I). 336-354. https://doi.org/10.1086/345949 ISSN: 0004-637X