- Damped Lyman-alpha system
Damped Lyman alpha systems or Damped Lyman alpha absorption systems are gaseous objects in the universe detected in the spectra of quasars, with a column density larger than 1020 atoms/cm2. The observed spectra consist of neutral hydrogen Lyman alpha absorption lines which are broadened by radiation damping. The systems are important because they can be identified at very large redshifts, the neutral gas in the universe is dominated by them and they are neutral which means no need for ionization corrections in the measurements. The high neutral hydrogen column densities of DLAs are also typical of sightlines in the Milky Way, and other nearby galaxies. DLAs are thus believed to be related to gas rich galaxies at all redshifts that they are seen.
- ^ Coles, Peter; Lucchin, Francesco (2002). Cosmology: The Origin and Evolution of Cosmic Structure (2nd ed.). England: John Wiley & Sons. pp. 430–432. ISBN 0471489093.
- ^ a b Lanzetta, Kenneth M (2001). "Lyman Alpha Absorption: The Damped Systems". Encyclopedia of Astronomy and Astrophysics. ISBN 0333750888.
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