Issue |
A&A
Volume 421, Number 3, July III 2004
|
|
---|---|---|
Page(s) | 969 - 976 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20035957 | |
Published online | 29 June 2004 |
A possible age-metallicity relation in the Galactic thick disk? *
Lund Observatory, Box 43, 221 00 Lund, Sweden e-mail: [sofia;ingemar]@astro.lu.se
Corresponding author: T. Bensby, thomas@astro.lu.se
Received:
30
December
2003
Accepted:
21
March
2004
A sample of 229 nearby thick disk stars has been
used to investigate the existence of an age-metallicity relation (AMR)
in the Galactic thick disk. The results indicate that that there is
indeed an age-metallicity relation present in the thick disk.
By dividing the stellar sample into sub-groups,
separated by 0.1 dex in metallicity, we show that the median age
decreases by about 5–7 Gyr when going
from [Fe/H] to [Fe/H]
. Combining
our results with our newly published α-element trends
for a local sample of thick disk stars that show
signatures from supernovae type Ia (SN Ia),
we draw the conclusion
that the time-scale for the peak of the SN Ia rate is of the order
of 3–4 Gyr in the thick disk. The tentative evidence for
a thick disk AMR that we present here also has implications for
the thick disk
formation scenario; star-formation must have been an ongoing
process for several billion years. This
appears to strengthen the hypothesis that the thick disk
originated from a merger event with a companion galaxy that puffed
up a pre-existing thin disk.
Key words: stars: Hertzsprung-Russell (HR) and C-M diagrams / stars: kinematics / Galaxy: disk / Galaxy: kinematics and dynamics / Galaxy: solar neighbourhood / Galaxy: formation
© ESO, 2004
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