1. Главная
  2. Ресурсы
  3. Библиотечный поиск
Abundances at HighRedshifts: TheChemical EnrichmentHistory OF Limin LuW. L. W. SargentT. A. Barlow1996 год

Abundances at High Redshifts: The Chemical Enrichment History OF
статья из журнала

Полный текстСтраница публикацииПубликация в OpenAlex
Аннотация: We study the elemental abundances of C, N, O, Al, Si, S, Cr, Mn, Fe, Ni, and Zn in a sample of 14 damped Lyα systems (galaxies) with H I column density N (H I)≥ 10 20 cm -2 , using high quality spectra of quasars obtained with the 10m Keck telescope.To ensure accuracy, only weak, unsaturated absorption lines are used to derive ion column densities and elemental abundances.Combining these abundance measurements with similar measurements in the literature, we investigate the chemical evolution of damped Lyα galaxies based on a sample of 23 systems in the redshift range 0.7 < z < 4.4.The main conclusions are as follows.1.The damped Lyα galaxies have (Fe/H) in the range of 1/10 to 1/300 solar, clearly indicating that these are young galaxies in the early stages of chemical evolution.The N (H I)-weighted mean metallicity of the damped Lyα galaxies between 2 < z < 3 is (Fe/H)=0.028solar.There is a large scatter, about a factor of 30, in (Fe/H) at z < 3, which we argue probably results from the different formation histories of the absorbing galaxies or a mix of galaxy types.2. Comparisons of the distribution of (Fe/H) vs redshift for the sample of damped Lyα galaxies with the similar relation for the Milky Way disk indicate that the damped Lyα galaxies are much less metal-enriched than the Galactic disk in its past.Since there is evidence from our analyses that depletion of Fe by dust grains in the sample galaxies is relatively unimportant, the difference in the enrichment level between the sample of damped Lyα galaxies and the Milky Way disk suggests that damped Lyα galaxies are probably not high-redshift spiral disks in the traditional sense.Rather, they could represent a thick disk phase of galaxies, or more likely the spheroidal component of galaxies, or dwarf galaxies.3. The mean metallicity of the damped Lyα galaxies is found to increase with decreasing redshift, as is expected.All four of the damped Lyα galaxies at z > 3 in our sample have (Fe/H) around 1/100 solar or less.In comparison, a large fraction of the damped Lyα galaxies at z < 3 have reached ten times higher metallicity.This suggests that the time around z = 3 may be the epoch of galaxy formation in the sense that galaxies are beginning to form the bulk of their stars.Several other lines of evidence appear to point to the same conclusion, including the evolution of the neutral baryon
Год издания: 1996
Авторы: Limin Lu, W. L. W. Sargent, T. A. Barlow, Damped Ly Galaxies, Christopher W. Churchill, Steven S. Vogt
Издательство: Institute of Physics
Источник: The Astrophysical Journal Supplement Series
Ключевые слова: Galaxies: Formation, Evolution, Phenomena, Astronomy and Astrophysical Research, Gamma-ray bursts and supernovae
Другие ссылки: The Astrophysical Journal Supplement Series (HTML)
arXiv (Cornell University) (PDF)
arXiv (Cornell University) (HTML)
DataCite API (HTML)