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- Bensby, Thomas, et al.
(författare)
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A Differential Study of the Oxygen Abundances in the Galactic Thin and Thick Disks
- 2004
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Ingår i: Carnegie Observatories Astrophysics Series, Origin and Evolution of the Elements. ; 4
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Konferensbidrag (refereegranskat)abstract
- First results from a study into the abundance trends of oxygen in the Galactic thin and thick disks are presented. Oxygen abundances for 63nearby F and G dwarf stars, based on very high resolution spectra (R∼215 000) and high signal-to-noise (S/N>400) of the faint forbidden oxygen line at 6300Å, have been determined. Our findings can be summarized as follows: 1) at [Fe/H]<0 the oxygen trends in thethin and thick disk are smooth and distinct, indicating their different origins, 2) [O/Fe] for the thick disk stars show a turn-over at[Fe/H]∼-0.35, indicating the peak of the enrichment from SNe type Ia to the interstellar medium, 3) the thin disk stars show a shallow decrease going from [Fe/H] ∼-0.7 to the highest metallicities with no apparent turn-over present indicating a more quiet star formation history, and 4) [O/Fe] continues to decrease at [Fe/H] > 0 without showing the leveling out that previously has been seen.
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- Bensby, Thomas, et al.
(författare)
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A Possible Bulge - Thick Disk Connection?
- 2003
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Ingår i: Elemental Abundances in Old Stars and Damped Lyman-alpha Systems. ; 15
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Konferensbidrag (refereegranskat)abstract
- We present abundances of giant stars in the Galactic bulge and thickdisk. The stellar sample contains approximately 15 bulge giants and 20thick disk giants observed with the UVES on VLT in Chile. These resultswill be used to see if there exists an evolutionary connection betweenthe bulge and the thick disk and will also put further light into theformation of the Milky Way and the thick disk in particular.
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- Bensby, Thomas, et al.
(författare)
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Chemical constraints on the formation of the Galactic thick disk
- 2012
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Ingår i: Assembling the Puzzle of the Milky Way. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 19
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Konferensbidrag (refereegranskat)abstract
- We highlight some results from our detailed abundance analysis study of 703 kinematically selected F and G dwarf stars in the solar neighbourhood. The analysis is based on spectra of high-resolution (R = 45 000 to 110 000) and high signal-to-noise (S/N approximate to 150 to 300). The main findings include: (1) at a given metallicity, the thick disk abundance trends are more alpha-enhanced than those of the thin disk; (2) the metal-rich limit of the thick disk reaches at least solar metallicities; (3) the metal-poor limit of the thin disk is around [Fe/H] approximate to -0.8; (4) the thick disk shows an age-metallicity gradient; (5) the thin disk does not show an age-metallicity gradient; (6) the most metal-rich thick disk stars at [Fe/H] approximate to 0 are significantly older than the most metal-poor thin disk stars at [Fe/H] approximate to -0.7; (7) based on our elemental abundances we find that kinematical criteria produce thin and thick disk stellar samples that are biased in the sense that stars from the low-velocity tail of the thick disk are classified as thin disk stars, and stars from the high-velocity tail of the thin disk are classified as thick disk stars; (8) age criteria appears to produce thin and thick disk stellar samples with less contamination.
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- Bensby, Thomas, et al.
(författare)
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Chemical Evolution of the Galactic Disk(s)
- 2012
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Ingår i: Galactic archeology, near-field cosmology and the formation of the Milky Way (ASP Conference Series). ; 458, s. 201-202
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Konferensbidrag (refereegranskat)abstract
- We highlight some results from our high-resolution spectroscopic elemental abundance survey of F and G dwarf stars in the solar neighbourhood.
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- Bensby, Thomas, et al.
(författare)
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Oxygen in the Galactic Thin and Thick Disks
- 2003
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Ingår i: CNO in the universe. (ASP Conference Series ; Vol. 304).. - 1583811532 ; 304, s. 175-178
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Konferensbidrag (refereegranskat)
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| 10. |
- Bensby, Thomas, et al.
(författare)
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Signatures of an Intermediate-Age Metal-Rich Bulge Population
- 2012
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Ingår i: Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way (Astronomical Society of the Pacific Conference Series). - 9781583817988 ; 458, s. 203-204
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Konferensbidrag (refereegranskat)abstract
- We have determined detailed elemental abundances and stellar ages for a sample of now 38 microlensed dwarf and subgiant stars in the Galactic bulge. Stars with sub-solar metallicities are all old and have enhanced alpha-element abundances - very similar to what is seen for local thick disk stars. The metal-rich stars on the other hand show a wide variety of stellar ages, ranging from 3-4 Gyr to 12 Gyr, and an average around 7-8 Gyr. The existence of young and metal-rich stars are in conflict with recent photometric studies of the bulge which claim that the bulge only contains old stars.
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