other query modes : |
Identifier query |
Coordinate query |
Criteria query |
Reference query |
Basic query |
Script submission |
TAP |
Output options |
Object types |
Help |
2000AJ....120.2513P - Astron. J., 120, 2513-2549 (2000/November-0)
The galactic thick disk stellar abundances.
PROCHASKA J.X., NAUMOV S.O., CARNEY B.W., McWILLIAM A. and WOLFE A.M.
Abstract (from CDS):
The principal results of our analysis are as follows. (1) All 10 stars exhibit enhanced α/Fe ratios with O, Si, and Ca showing tentative trends of decreasing overabundances with increasing [Fe/H]. In contrast, the Mg and Ti enhancements are constant. (2) The light elements Na and Al are enhanced in these stars. (3) With the exception of Ni, Cr, and possibly Cu, the iron-peak elements show significant departures from the solar abundances. The stars are deficient in Mn, but overabundant in V, Co, Sc, and Zn. (4) The heavy elements Ba and Y are consistent with solar abundances, but Eu is significantly enhanced. If the trends of decreasing O, Si, and Ca with increasing [Fe/H] are explained by the onset of Type Ia SN, then the thick disk stars formed over the course of ≳1 Gyr. We argue that this formation time-scale would rule out most dissipational collapse scenarios for the formation of the thick disk. Models which consider the heating of an initial thin disk–either through ``gradual'' heating mechanisms or a sudden merger event–are favored. These observations provide new tests of theories of nucleosynthesis in the early universe. In particular, the enhancements of Sc, V, Co, and Zn may imply overproduction during an enhanced α-rich freeze out fueled by neutrino-driven winds. Meanwhile, the conflicting trends for Mg, Ti, Ca, Si, and O pose a difficult challenge to our current understanding of nucleosynthesis in Type Ia and Type II SN. The Ba/Eu ratios favor r-process dominated enrichment for the heavy elements, consistent with the ages (tage>10 Gyr) expected for these stars.
Finally, we discuss the impact of the thick disk abundances on interpretations of the abundance patterns of the damped Lyα systems. The observations of mildly enhanced Zn/Fe imply an interpretation for the damped systems which includes a dust depletion pattern on top of a Type II SN enrichment pattern. We also argue that the S/Zn ratio is not a good indicator of nucleosynthetic processes.
Abstract Copyright: ∼
Journal keyword(s): Galaxy: Abundances - Galaxy: Formation– - Stars: Abundances
Simbad objects: 16
To bookmark this query, right click on this link: simbad:2000AJ....120.2513P and select 'bookmark this link' or equivalent in the popup menu