AAS 200th meeting, Albuquerque, NM, June 2002
Session 40. Evolution of Galaxies, Galaxy Surveys, IGM
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

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[40.18] Science from the refurbished FOS/BLUE archive: Interstellar absorption lines in a sample of low red-shift quasars

F. Kerber (ST-ECF), B. Wills (UT, Austin), A. Alexov, P. Bristow (ST-ECF), A. Seifarth (Univ. Jena), M.R. Rosa (ST-ECF)

We have studied the velocities of the interstellar absorption lines imprinted on a sample of 14 quasars. The post-operational archive (POA) project conducted at the ST-ECF has led to very significant improvements in the calibration of the HST's Faint Object Spectrograph (FOS). In particular systematic errors in the wavelength scale amounting to up to 400\,km/s at 1200\,{Å} have been removed and the improved wavelength calibration is now accurate to about 50\,km/s. Evidently such an improvement is of vital importance for the velocity studies of interstellar absorption lines. Using G130H spectra we find velocities of between 10 and -120\,km/s (relative to the LSR) for the UV absorption lines of ionized metals, like Si\,II, Si\,III, Si\,IV, C\,II and C\,IV. Despite the limited resolution we find that the velocity of the UV absorption usually does not not coincide with the peaks in the 21\,cm Hydrogen emission. This indicates that the lines probably come from physically distinct regions. This is also in agreement with our understanding of the distribution of different phases of the ISM in the Galactic disk, where neutral and ionized regions co-exist and any line of sight is likely to cross more than one phase.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.