J/ApJ/749/175 Abundances for stars in Plaut's window (Johnson+, 2012)
Constraints on the formation of the Galactic bulge from Na, Al, and
heavy-element abundances in Plaut's field.
Johnson C.I., Rich R.M., Kobayashi C., Fulbright J.P.
<Astrophys. J., 749, 175 (2012)>
=2012ApJ...749..175J 2012ApJ...749..175J
ADC_Keywords: Abundances ; Stars, giant
Keywords: Galaxy: bulge - stars: abundances - stars: Population II
Abstract:
We report chemical abundances of Na, Al, Zr, La, Nd, and Eu for 39 red
giant branch (RGB) stars and 23 potential inner disk red clump stars
located in Plaut's low-extinction window. We also measure lithium for
a super Li-rich RGB star. The abundances were determined by spectrum
synthesis of high-resolution (R~25000), high signal-to-noise
(S/N ∼ 50-100/pixel) spectra obtained with the Blanco 4m telescope and
Hydra multifiber spectrograph. For the bulge RGB stars, we find a
general increase in the [Na/Fe] and [Na/Al] ratios with increasing
metallicity, and a similar decrease in [La/Fe] and [Nd/Fe].
Additionally, the [Al/Fe] and [Eu/Fe] abundance trends almost
identically follow those of the α-elements, and the [Zr/Fe]
ratios exhibit relatively little change with [Fe/H]. The consistently
low [La/Eu] ratios of the RGB stars indicate that at least a majority
of bulge stars formed rapidly (≲1Gyr) and before the main s-process
could become a significant pollution source. In contrast, we find that
the potential inner disk clump stars exhibit abundance patterns more
similar to those of the thin and thick disks. Comparisons between the
abundance trends at different bulge locations suggest that the inner
and outer bulges formed on similar timescales. However, we find
evidence of some abundance differences between the most metal-poor and
metal-rich stars in various bulge fields. The data also indicate that
the halo may have had a more significant impact on the outer bulge
initial composition than the inner bulge composition. The [Na/Fe], and
to a lesser extent [La/Fe], abundances further indicate that the
metal-poor bulge, at least at ∼1 kpc from the Galactic center, and
thick disk may not share an identical chemistry.
Description:
Details of the target selection, observations, data reductions, and
previous abundance determinations are provided in Johnson et al.
(2011, Cat. J/ApJ/732/108):
We have previously obtained high-resolution (R∼25000), high
signal-to-noise (S/N∼50-100pixel-1) spectra of a combined 92 stars
in two separate fields located near Plaut's low-extinction window. All
data were obtained using the Blanco 4m telescope instrumented with the
Hydra multifiber spectrograph at Cerro Tololo Inter-American
Observatory during two separate runs spanning 2006 May 27-28 and 2007
May 19-23.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 81 62 Model atmosphere parameters and abundance ratios
table3.dat 54 372 Error estimation
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/A+A/546/A57 : Spectro. of 400 red giants in the Bulge (Uttenthaler+, 2012)
J/ApJ/732/108 : Pap I. 92 giants abundances in Plaut's window (Johnson+, 2011)
J/A+A/513/A35 : Abundances of Galactic red giants (Alves-Brito+, 2010)
J/A+A/465/799 : Abundances of Galactic Bulge red giants (Lecureur+, 2007)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs; J2000)
18- 21 I4 K Teff [4000/4950] Effective temperature
23- 26 F4.2 [cm/s2] logg [0.8/2.5] Surface gravity
28- 32 F5.2 [Sun] [Fe/H] [-1.6/0.5] Metallicity
34- 37 F4.2 km/s Vt [1.1/2.1] Turbulent velocity
39- 43 F5.2 [Sun] [Na/Fe] [-0.7/0.6]? [Na/Fe] abundance
45- 49 F5.2 [Sun] [Al/Fe] [-0.6/0.6]? [Al/Fe] abundance
51- 55 F5.2 [Sun] [Zr/Fe] [-0.5/1.2]? [Zr/Fe] abundance
57- 61 F5.2 [Sun] [La/Fe] [-0.6/1.5]? [La/Fe] abundance
63- 67 F5.2 [Sun] [Nd/Fe] [-0.5/1.3]? [Nd/Fe] abundance
69- 73 F5.2 [Sun] [Eu/Fe] [-0.3/1]? [Eu/Fe] abundance
75- 79 A5 --- Type [RGB Clump] RGB=probable RGB member;
Clump=probable red clump star member
81 I1 --- Field [1/2] Field number (1)
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Note (1): Field number (see Johnson et al. 2011, Cat. J/ApJ/732/108)
for details:
1 = Field 1 (l=-1°, b=-8.5°);
2 = Field 2 (l=0°, b=-8°);
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 A1 --- Type [a-f] Type of variation (1)
3- 18 A16 --- 2MASS 2MASS identification (HHMMSSss+DDMMSSs; J2000)
20- 24 F5.2 [Sun] d[Na/Fe] [-0.2/0.3]? [Na/Fe] variation with Type
26- 30 F5.2 [Sun] d[Al/Fe] [-0.2/0.3]? [Al/Fe] variation with Type
32- 36 F5.2 [Sun] d[Zr/Fe] [-0.4/0.5]? [Zr/Fe] variation with Type
38- 42 F5.2 [Sun] d[La/Fe] [-0.3/0.4]? [La/Fe] variation with Type
44- 48 F5.2 [Sun] d[Nd/Fe] [-0.2/0.3]? [Nd/Fe] variation with Type
50- 54 F5.2 [Sun] d[Eu/Fe] [-0.1/0.3]? [Eu/Fe] variation with Type
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Note (1): Flag indicating the model atmosphere parameter variation
(see section 2.2 for further explanations):
a = ΔTeff = +100K
b = Δlog(g) = +0.3dex
c = Δ[M/H] = +0.3dex
d = ΔVt = +0.3km/s
e = Line-to-line dispersion. A value of 0.07dex (the average line-to-line
dispersion for all elements where more than one line was measured) was
set for elements and/or stars where only a single line was available.
f = Total uncertainty: (Σσ2)0.5
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History:
From electronic version of the journal
Reference:
Johnson et al. Paper I. 2011ApJ...732..108J 2011ApJ...732..108J Cat. J/ApJ/732/108
(End) Emmanuelle Perret [CDS] 02-Dec-2013