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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 81 62 Model atmosphere parameters and abundance ratios table3.dat 54 372 Error estimation
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
Bytes Format Units Label Explanations
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)
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°);
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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
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
History: From electronic version of the journal Reference: Johnson et al. Paper I. 2011ApJ...732..108J Cat. J/ApJ/732/108
(End) Emmanuelle Perret [CDS] 02-Dec-2013
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