Nitrogen Abundances in Damped Lyα Galaxies

作者：Miriam Centurion, Piercarlo Bonifacio, Paolo Molaro, Giovanni Vladilo · 发表于：The Astrophysical Journal · 年份：1998 · DOI：10.1086/306537 · 被引用次数：33 · 研究领域：Galaxies: Formation, Evolution, Phenomena、Astronomy and Astrophysical Research、Stellar, planetary, and galactic studies

Nitrogen lines of the N I λ1134 and λ1200 multiplets in the damped Lyα (DLA) galaxies at z abs = 2.309, 2.827, and 3.025 toward the QSOs 0100+1300, 1425+6039, and 0347-3819, respectively, have been detected by means of high-resolution spectra ( R ~ 2 × 10 4 ) obtained with 4 m class telescopes at ESO (La Silla, Chile) and the Observatorio del Roque de los Muchachos (La Palma, Spain). The two N I multiplets offer a considerable range in oscillator strengths and the possibility of disentangling Lyα interlopers. The derived nitrogen abundances for the three damped systems are [N/H] = -2.68 ± 0.11, -1.57 ± 0.09, -2.07 ± 0.13, respectively. The behavior of nitrogen relative to iron-peak and α elements has been investigated by considering all the extant N I determinations for a total of nine DLA galaxies. We have estimated the fraction of iron locked into dust grains to convert the observed [N/Fe] ratios into overall (dust plus gas) relative abundances, [N/Fe] corr . The ratios [N/α] have been mostly determined by using sulphur as a tracer of α elements that is unaffected by dust. The [N/Fe] and [N/α] ratios show high dispersions, of 1 order of magnitude or more, which have no equivalent in other element-to-element ratios in DLAs. The lowest values of the [N/Fe] corr and [N/α] ratios are at variance with the values measured in Galactic halo stars of similar metallicity, suggesting that part of the DLA galaxies do not follow the chemical evolution of the Milky Way. The DLA nitrogen ...