Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989apj...342..666e&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 342, July 15, 1989, p. 666-676.
Astronomy and Astrophysics
Astrophysics
143
Astronomical Spectroscopy, Emission Spectra, H Alpha Line, Quasars, Cosmochemistry, Red Shift, Spectrum Analysis
Scientific paper
Infrared spectra have been obtained of the H-alpha lines in 18 medium- to high-redshift QSOs and optical spectra taken nearly simultaneously to measure the strong UV line. It is found that the H-alpha line is redshifted by an average of 1000 km/s with respect to the lines from high ionization species such as C IV. Low ionization lines from ions like O I and Mg II are shifted by similar, or slightly smaller, amounts with respect to the high ionization lines. These results are difficult to reconcile with any simple models currently available, including those where dust obscuration is solely responsible for the observed velocity shifts. The similarity between the velocities of H-alpha and Mg II, O I provides some support for models in which the Balmer lines are produced predominantly in a warm H I region, while the Lyman lines arise mainly in a population of optically thin clouds. A velocity separation between the two cloud populations, along with some obscuration, could explain the main features.
Bailey Jon A.
Carswell Robert F.
Espey Brian R.
Smith Malcolm G.
Ward Martin J.
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