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Titolo:
Nitrogen abundances in damped Ly alpha galaxies
Autore:
Centurion, M; Bonifacio, P; Molaro, P; Vladilo, G;
Indirizzi:
Inst Astrofis Canarias, Tenerife 38200, Spain Inst Astrofis Canarias Tenerife Spain 38200 arias, Tenerife 38200, Spain Osservatorio Astron Trieste, I-34131 Trieste, Italy Osservatorio Astron Trieste Trieste Italy I-34131 I-34131 Trieste, Italy
Titolo Testata:
ASTROPHYSICAL JOURNAL
fascicolo: 2, volume: 509, anno: 1998,
parte:, 1
pagine: 620 - 632
SICI:
0004-637X(199812)509:2<620:NAIDLA>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
NEAR-INFRARED SPECTROSCOPY; HUBBLE-SPACE-TELESCOPE; HIGH-REDSHIFT GALAXIES; H-II REGIONS; ABSORPTION SYSTEMS; CHEMICAL EVOLUTION; ELEMENT ABUNDANCES; METAL ENRICHMENT; DWARF GALAXIES; STAR-FORMATION;
Keywords:
galaxies : abundances; galaxies : ISM; quasars : absorption lines; ultraviolet : galaxies;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
75
Recensione:
Indirizzi per estratti:
Indirizzo: Centurion, M Inst Astrofis Canarias, Tenerife 38200, Spain Inst Astrofis Canarias Tenerife Spain 38200 fe 38200, Spain
Citazione:
M. Centurion et al., "Nitrogen abundances in damped Ly alpha galaxies", ASTROPHYS J, 509(2), 1998, pp. 620-632

Abstract

Nitrogen lines of the N I lambda 1134 and lambda 1200 multiplets in the damped Ly alpha (DLA) galaxies at z(abs) = 2.309, 2.827, and 3.025 toward theQSOs 0100+1300, 1425+6039, and 0347-3819, respectively, have been detectedby means of high-resolution spectra (R similar to 2 x 10(4)) obtained with4 m class telescopes at ESO (La Silla, Chile) and the Observatorio del Rogue de los Muchachos (La Palma, Spain). The two N I multiplets offer a considerable range in oscillator strengths and the possibility of disentangling Lya 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 alpha elements has been investigated by considering all the extant N I determinations for a totalof 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/alpha] have been mostlydetermined by using sulphur as a tracer of a elements that is unaffected by dust. The [N/Fe] and [N/alpha] 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/alpha] 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 abundances and their dispersion show some similarities with those observed in dwarf galaxies. Comparison with chemical evolution models shows that the lowest [N/Fe](corr) and [N/alpha] DLA values are close to what would be expected for a pure secondary origin of nitrogen, whereas higher values are mostly consistent with a primary component. The behavior of nitrogen abundance ratios can be ascribed, in general, to the delayed release of nitrogen in the course of evolution. However it is difficult to conciliate this interpretation with the lowest[N/alpha] values measured, since an expected enhancement of alpha elementswith respect to the iron-peak elements is not observed simultaneously in these DLA galaxies. In two cases, relatively high [N/alpha] values are observed that require also a more complex chemical evolution to be explained.

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Documento generato il 24/09/20 alle ore 08:23:45