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C.E. Flack (Bemidji State University), B.P. Wakker (University of Wisconsin - Madison)
We determined metallicites and abundances for several high- and intermediate- velocity clouds (HVCs and IVCs), using spectra from the FUSE satellite and the STIS and HRS spectrographs on the HST. We measured absorption lines of several elements, including OI, NI, SiII, and FeII. HI column densities were derived from 21 cm emission data, in order to calculate the abundances of each detected element. The sightlines to ESO265-G23 and NGC5253 are through Complex WD, a group of positive velocity HVCs, with v~120km/s; and PG1011-040 samples Complex WB, another positive velocity HVC in the same region. Although these sightlines have similar HI characteristics, NGC5253 yields nearly solar abundances, while the other two sightlines give Z~0.1 solar. Mrk509 was a sightline though complex gp, a positive velocity IVC with abundances ~0.3 solar. Mrk205 is a sightline through WW84, one of the few compact high-velocity clouds (CHVCs) with a known background target. The abundances of this cloud are ~0.1 solar but are fairly uncertain. From the results given here, it is apparent that HVCs and IVCs have a diverse range of abundances and therefore differing origins. In this study we have identified several more examples of both low-metallicity inflow and possible galactic fountain clouds.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.