J/ApJ/735/L46 Spectroscopy of 64 K red giants (Bensby+, 2011)
A first constraint on the thick disk scale length: differential radial
abundances in K giants at Galactocentric radii 4, 8, and 12 kpc.
Bensby T., Alves-Brito A., Oey M.S., Yong D., Melendez J.
<Astrophys. J., 735, L46 (2011)>
=2011ApJ...735L..46B 2011ApJ...735L..46B
ADC_Keywords: Abundances ; Milky Way ; Radial velocities ; Stars, giant ;
Stars, distances ; Stars, K-type
Keywords: Galaxy: abundances - Galaxy: disk - Galaxy: evolution -
Galaxy: formation - Galaxy: stellar content - stars: abundances
Abstract:
Based on high-resolution spectra obtained with the MIKE spectrograph
on the Magellan telescopes, we present detailed elemental abundances
for 20 red giant stars in the outer Galactic disk, located at
Galactocentric distances between 9 and 13kpc. The outer disk sample is
complemented with samples of red giants from the inner Galactic disk
and the solar neighborhood, analyzed using identical methods. For
Galactocentric distances beyond 10kpc, we only find chemical patterns
associated with the local thin disk, even for stars far above the
Galactic plane. Our results show that the relative densities of the
thick and thin disks are dramatically different from the solar
neighborhood, and we therefore suggest that the radial scale length of
the thick disk is much shorter than that of the thin disk. We make a
first estimate of the thick disk scale length of Lthick=2.0kpc,
assuming Lthin=3.8kpc for the thin disk. We suggest that radial
migration may explain the lack of radial age, metallicity, and
abundance gradients in the thick disk, possibly also explaining the
link between the thick disk and the metal-poor bulge.
Description:
Twenty red giants in the outer disk, selected from the Two Micron All
Sky Survey catalog, were observed with the MIKE spectrograph on the
Magellan telescopes in 2007 November. Table 1 gives the stellar
parameters, kinematics, and elemental abundances for the 20 outer disk
giants and the 44 inner disk giants from Bensby et al.
(2010A&A...516L..13B 2010A&A...516L..13B); see this reference for the sample selection,
instrumental setup, data reduction, abundance analysis, determination
of distances, space velocities, and orbital parameters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 102 64 Stellar parameters, kinematics, and abundances
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/A+A/546/A57 : Structure and formation of the Bulge (Uttenthaler+, 2012)
J/A+A/534/A136 : Halo red giants from the SEGUE survey (Martell+, 2011)
J/A+A/513/A35 : Abundances of Galactic red giants (Alves-Brito+, 2010)
J/A+A/512/A41 : Abundances of microlensed stars in the Bulge (Bensby+, 2010)
J/A+A/465/799 : Abundances of Galactic Bulge red giants (Lecureur+, 2007)
J/AJ/132/902 : Abundances of 54 Cepheids (Luck+, 2006)
J/MNRAS/367/1329 : Elemental abundances for 176 stars (Reddy+, 2006)
J/AJ/130/1111 : Elemental abundances of field red giants (Carney+, 2005)
J/A+A/413/159 : Galactic abundance gradient. V. (Andrievsky+, 2004)
J/A+A/433/185 : Detailed abundance analysis of F and G dwarfs (Bensby+, 2005)
J/A+A/415/155 : Oxygen abundances in the Galactic disk (Bensby+, 2004)
J/A+A/410/527 : Abundances in the Galactic disk (Bensby+, 2003)
J/AJ/109/1095 : Thick Disk Chemical Abundance Distribution (Gilmore+ 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- 2MASS The 2MASS identification (HHMMSSss+DDMMSSs; J2000)
19- 23 F5.1 deg GLON Galactic longitude
26- 30 F5.1 deg GLAT Galactic latitude
33- 37 I5 pc Dist [859/12930] Distance from the Sun
39- 44 F6.1 km/s HRV Heliocentric radial velocity
48- 51 I4 km/s ULSR ? U velocity relative to LSR
55- 58 I4 km/s VLSR ? V velocity relative to LSR
62- 65 I4 km/s WLSR ? W velocity relative to LSR
69- 72 I4 K Teff [3800/4600] Effective temperature
76- 78 F3.1 [cm/s2] log(g) [0.1/2.4] Log of the surface gravity
80- 84 F5.2 [Sun] [Fe/H] The [Fe/H] abundance ratio relative to the Sun
86- 90 F5.2 [Sun] [Mg/Fe] The [Mg/Fe] abundance ratio relative to the Sun
92- 96 F5.2 [Sun] [Si/Fe] ? The [Si/Fe] abundance ratio relative to the Sun
98-102 F5.2 [Sun] [Ti/Fe] The [Ti/Fe] abundance ratio relative to the Sun
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Dec-2012