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Titolo:
Chemical evolution of damped Ly alpha galaxies: The [S/Zn] abundance ratioat redshift >= 2
Autore:
Centurion, M; Bonifacio, P; Molaro, P; Vladilo, G;
Indirizzi:
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: 536, anno: 2000,
parte:, 1
pagine: 540 - 549
SICI:
0004-637X(20000620)536:2<540:CEODLA>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
SURFACE-BRIGHTNESS GALAXIES; ELEMENTAL ABUNDANCES; DISK STARS; SYSTEMS; HALO; DUST; METALLICITY; ENRICHMENT; DISCOVERY; NITROGEN;
Keywords:
cosmology : observations; galaxies : abundances; galaxies : evolution; quasars : absorption lines;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
38
Recensione:
Indirizzi per estratti:
Indirizzo: Centurion, M Osservatorio Astron Trieste, Via GB Tiepolo 11, I-34131 Trieste, Italy Osservatorio Astron Trieste Via GB Tiepolo 11 Trieste Italy I-34131
Citazione:
M. Centurion et al., "Chemical evolution of damped Ly alpha galaxies: The [S/Zn] abundance ratioat redshift >= 2", ASTROPHYS J, 536(2), 2000, pp. 540-549

Abstract

Relative elemental abundances, and in particular the alpha/Fe ratio, are important diagnostic tools of the chemical evolution of damped Ly alpha (DLA) systems. The S/Zn ratio is not affected by differential, dust depletion and is an excellent estimator of the alpha/Fe ratio. We report six new determinations of sulphur abundance in DLA systems at z(abs) greater than or equal to 2 with already-known zinc abundances. The combination with extant data from the literature provides a measure of the S/Zn abundance ratio for a total of 11 high-redshift DLA systems. The observed [S/Zn] ratios do not show the characteristic [alpha/Fe] enhancement observed in metal-poor stars of the Milky Way at a comparable level of metallicity ([Zn/H] approximate to- 1). The behavior of DLA data is consistent with a general trend of a decreasing [S/Zn] ratio with increasing metallicity [Zn/H]. This would be the first evidence of the expected decrease of the alpha/Fe ratio in the courseof the chemical evolution of DLA systems. However, in contrast to what is observed in our Galaxy, the alpha/iron peak ratio seems to attain solar values when the metallicity is still low ([Zn/H] less than or equal to - 1) and to decrease below solar values at higher metallicities. The behavior of the alpha/Fe ratio challenges the frequently adopted hypothesis that high-redshift DLA systems are progenitors of spiral galaxies and instead favors anorigin in galaxies characterized by low star formation rates, in agreementwith the results from imaging studies of low-redshift DLA systems, where the candidate DLA galaxies show a variety of morphological types, including dwarf and low surface brightness galaxies and only a minority of spirals.

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Documento generato il 24/09/20 alle ore 07:09:03