J/AJ/148/67 Abundances of 156 bulge red giants (Johnson+, 2014)
Light, alpha, and Fe-peak element abundances in the Galactic bulge.
Johnson C.I., Rich R.M., Kobayashi C., Kunder A., Koch A.
<Astron. J., 148, 67 (2014)>
=2014AJ....148...67J 2014AJ....148...67J
ADC_Keywords: Milky Way ; Stars, giant ; Abundances ; Radial velocities ;
Effective temperatures
Keywords: Galaxy: bulge - stars: abundances - stars: Population II
Abstract:
We present radial velocities and chemical abundances of O, Na, Mg, Al,
Si, Ca, Cr, Fe, Co, Ni, and Cu for a sample of 156 red giant branch
stars in two Galactic bulge fields centered near (l,b)=(+5.25,-3.02)
and (0,-12). The (+5.25,-3.02) field also includes observations of the
bulge globular cluster NGC 6553. The results are based on
high-resolution (R∼20000), high signal-to-noise ration (S/N≳70)
FLAMES-GIRAFFE spectra obtained through the European Southern
Observatory archive. However, we only selected a subset of the
original observations that included spectra with both high S/N and
that did not show strong TiO absorption bands. This work extends
previous analyses of this data set beyond Fe and the α-elements
Mg, Si, Ca, and Ti. While we find reasonable agreement with past work,
the data presented here indicate that the bulge may exhibit a
different chemical composition than the local thick disk, especially
at [Fe/H]≳-0.5. In particular, the bulge [α/Fe] ratios may
remain enhanced to a slightly higher [Fe/H] than the thick disk, and
the Fe-peak elements Co, Ni, and Cu appear enhanced compared to the
disk. There is also some evidence that the [Na/Fe] (but not [Al/Fe])
trends between the bulge and local disk may be different at low and
high metallicity. We also find that the velocity dispersion decreases
as a function of increasing [Fe/H] for both fields, and do not detect
any significant cold, high-velocity populations. A comparison with
chemical enrichment models indicates that a significant fraction of
hypernovae may be required to explain the bulge abundance trends, and
that initial mass functions that are steep, top-heavy (and do not
include strong outflow), or truncated to avoid including contributions
from stars >40M☉ are ruled out, in particular because of
disagreement with the Fe-peak abundance data. For most elements, the
NGC 6553 stars exhibit abundance trends nearly identical to comparable
metallicity bulge field stars. However, the star-to-star scatter and
mean [Na/Fe] ratios appear higher in the cluster, perhaps indicating
additional self-enrichment.
Description:
The FLAMES-GIRAFFE spectra for this project are based on data
obtained from the European Southern Observatory (ESO) Science Archive
Facility under request number 51251, which are based on observations
collected at the ESO, Paranal, Chile (ESO Program 073.B-0074).
Details regarding the selection of targets and input parameters (e.g.,
photometry and astrometry) are given in Zoccali et al. 2008 (cat.
J/A+A/486/177). To briefly summarize, fibers were placed on K giants
approximately 1-2mag brighter than the bulge red clump, and the
spectra were obtained in high-resolution mode
(R=λ/Δλ∼20000). The original program by Zoccali et
al. 2008 (cat. J/A+A/486/177) included four fields centered at
(l,b)=(+1.14,-4.18), (+0.21,-6.02), (0,-12), and (+5.25,-3.02). While
the (+1.14,-4.18) and (+0.21,-6.02) fields were observed in the HR 13,
HR 14, and HR 15 setups (spanning ∼6100-6950Å), the (+5.25,-3.02)
and (0,-12) fields were observed in the HR 11, HR 13, and HR 15 setups
(5590-5835Å; 6100-6400Å; 6600-6950Å). Since the HR 11 setup
is the only one containing measurable copper lines, we have only
analyzed GIRAFFE spectra from the (+5.25,-3.02) and (0,-12) fields. We
note that the (+5.25,-3.02) field also includes the bulge globular
cluster NGC 6553.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 126 156 Star identifications, coordinates, model
atmosphere parameters, and radial velocities
table2.dat 54 202 Line list
table3.dat 92 156 Abundance ratios
table4.dat 80 156 Total abundance uncertainty for ΔTeff+100K;
Δlog(g)+0.3cgs; Δ[M/H]+0.15dex;
Δvt+0.3km/s
table5.dat 80 156 1σ line-to-line abundance dispersion
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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)
II/213 : OGLE Galactic Bulge periodic variables (Udalski+ 1996)
I/244 : OGLE General Catalog of Stars. I. (Szymanski+ 1996)
J/A+A/563/A15 : Metallicity and kinematics in Galactic bar (Babusiaux+, 2014)
J/A+A/562/A66 : GIRAFFE Inner Bulge Survey (GIBS). I. (Zoccali+, 2014)
J/A+A/549/A147 : Abundances of microlensed Bulge dwarfs. V. (Bensby+, 2013)
J/ApJ/765/157 : Abundances of red giants in Galactic bulge (Johnson+, 2013)
J/ApJ/749/175 : Abundances for stars in Plaut's window (Johnson+, 2012)
J/A+A/546/A57 : Spectroscopy of 400 red giants in Bulge (Uttenthaler+, 2012)
J/ApJ/732/108 : Abundances of 92 giants in Plaut's window (Johnson+, 2011)
J/A+A/530/A54 : Abundances of 650 bulge red giants (Gonzalez+, 2011)
J/A+A/513/A35 : Abundances of Galactic red giants (Alves-Brito+, 2010)
J/ApJ/721/L28 : Red clump stars in Galactic Bulge from OGLE-III (Nataf+, 2010)
J/ApJ/699/66 : Abundances in two Galactic bulge stars (Cohen+, 2009)
J/ApJ/691/1387 : Spectroscopy of the Galactic bar. I. (Rangwala+, 2009)
J/ApJ/682/1029 : Abundances in OGLE-2007-BLG-349S (Cohen+, 2008)
J/A+A/486/177 : Bulge field stars from FLAMES-GIRAFFE spectra (Zoccali+, 2008)
J/A+A/465/799 : Abundances of Galactic Bulge red giants (Lecureur+, 2007)
J/ApJ/655/L33 : High-resolution spectrum of OGLE-2006-BLG-265 (Johnson+, 2007)
J/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004)
J/A+A/410/527 : Abundances in the Galactic disk (Bensby+, 2003)
J/AcA/52/217 : OGLE VI photometry of Galactic Bulge (Udalski+, 2002)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Field Galactic bulge field (G1)
13- 20 A8 --- OGLE OGLE identification value (G2)
22- 37 A16 --- 2MASS ? 2MASS identification
39- 48 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
50- 59 F10.6 deg DEdeg Declination in decimal degrees (J2000)
61- 65 F5.2 mag Vmag [14.97/16.25]? V-band magnitude
67- 71 F5.3 mag V-I [1.097/1.679]? The (V-I) color index
73- 78 F6.3 mag Jmag [11.71/13.854]? 2MASS J band magnitude
80- 85 F6.3 mag Hmag [10.794/13.357]? 2MASS H band magnitude
87- 92 F6.3 mag Ksmag [10.483/13.339]? 2MASS Ks band magnitude
94- 97 I4 K Teff [4225/5350] Effective temperature
99-102 F4.2 [cm/s2] logg [1.35/3.85] Surface gravity (cgs units)
104-108 F5.2 [Sun] [Fe/H] [-1.74/0.48] Metallicity (1)
110-113 F4.2 km/s vt [0.9/2.2] Microturbulent velocity
115-121 F7.2 km/s HRV [-280.09/255.23] Heliocentric radial velocity (2)
123-126 F4.2 km/s e_HRV [0.01/0.71] Error in HRV (3)
--------------------------------------------------------------------------------
Note (1): These [Fe/H] values are the average of the [FeI/H] and [FeII/H]
abundances given in Table 3. However, the average difference in the sense
[FeI/H]-[FeII/H] is +0.00dex with a small dispersion (σ=0.02dex).
Note (2): Represent the average value of all exposures and filters for each
star.
Note (3): The radial velocity errors represent the 1σ values from
individual exposures of each star over all filters.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Species
7- 14 A8 --- Col Name of the column in Table 3 giving the
ion abundance (added at CDS)
16- 22 F7.2 0.1nm lambda [5593.73/6864.31] Wavelength λ
24- 27 F4.2 eV EP [0/5.87] Excitation potential
29- 34 F6.3 [-] loggf [-9.75/-0.17]? Log of the oscillator strength
36- 38 A3 --- n_loggf [hfs] "hfs" indicates the hyperfine structure
was taken into account
(see Section 3.3 for details)
40- 43 F4.2 [-] logEsun [4.04/8.69] Derived solar abundance
logε(X)☉ (1)
45- 48 F4.2 [-] logEarc [3.71/8.63] Adopted Arcturus abundance
logε(X)Arc (1)
50- 54 F5.2 [Sun] Abund [-0.5/0.44] Abundance [X/Fe] or [Fe/H]Arc
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Note (1): Based on measurements of the Hinkle et al. (2000vnia.book.....H 2000vnia.book.....H)
Arcturus and solar atlases. The derived solar abundances for Fe, Si, Ca,
and Cr agree within ∼0.05dex of the values given in Asplund et al.
(2009ARA&A..47..481A 2009ARA&A..47..481A).
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Field Galactic bulge field (G1)
13- 20 A8 --- OGLE OGLE identification value (G2)
22- 26 F5.2 [Sun] [O/Fe] ? Log oxygen abundance relative to iron (4)
28- 32 F5.2 [Sun] [Na/Fe] Log sodium abundance relative to iron
34- 38 F5.2 [Sun] [Mg/Fe] ? Log magnesium abundance relative to iron
40- 44 F5.2 [Sun] [Al/Fe] ? Log aluminium abundance relative to iron
46- 50 F5.2 [Sun] [Si/Fe] Log silicon abundance relative to iron
52- 56 F5.2 [Sun] [Ca/Fe] Log calcium abundance relative to iron
58- 62 F5.2 [Sun] [Cr/Fe] ? Log chromium abundance relative to iron
64- 68 F5.2 [Sun] [FeI/H] Log metallicity derived from FeI lines
70- 74 F5.2 [Sun] [FeII/H] ? Log metallicity derived from FeII lines
76- 80 F5.2 [Sun] [Co/Fe] ? Log cobalt abundance relative to iron
82- 86 F5.2 [Sun] [Ni/Fe] Log nickel abundance relative to iron
88- 92 F5.2 [Sun] [Cu/Fe] ? Log copper abundance relative to iron
--------------------------------------------------------------------------------
Note (4): The [O/Fe] ratio is normalized to the [FeII/H] abundance. For stars
without an [FeII/H] measurement, the [O/Fe] ratio was normalized to the
[FeI/H] abundance.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Field Galactic bulge field (G1)
13- 20 A8 --- OGLE OGLE identification value (G2)
22- 25 F4.2 [Sun] dO ? Total uncertainty for [O/Fe] Δ[O/Fe] (5)
27- 30 F4.2 [Sun] dNa Total uncertainty for [Na/Fe] Δ[Na/Fe] (5)
32- 35 F4.2 [Sun] dMg ? Total uncertainty for [Mg/Fe]
Δ[Mg/Fe] (5)
37- 40 F4.2 [Sun] dAl ? Total uncertainty for [Al/Fe]
Δ[Al/Fe] (5)
42- 45 F4.2 [Sun] dSi Total uncertainty for [Si/Fe] Δ[Si/Fe] (5)
47- 50 F4.2 [Sun] dCa Total uncertainty for [Ca/Fe] Δ[Ca/Fe] (5)
52- 55 F4.2 [Sun] dCr ? Total uncertainty for [Cr/Fe]
Δ[Cr/Fe] (5)
57- 60 F4.2 [Sun] dFeI Total uncertainty for [FeI/H] Δ[FeI/H] (5)
62- 65 F4.2 [Sun] dFeII ? Total uncertainty for [FeII/H]
Δ[FeII/H] (5)
67- 70 F4.2 [Sun] dCo ? Total uncertainty for [Co/Fe]
Δ[Co/Fe] (5)
72- 75 F4.2 [Sun] dNi Total uncertainty for [Ni/Fe] Δ[Ni/Fe] (5)
77- 80 F4.2 [Sun] dCu ? Total uncertainty for [Cu/Fe]
Δ[Cu/Fe] (5)
--------------------------------------------------------------------------------
Note (5): We investigated the sensitivity of derived abundances for each element
in every star by taking the abundances given in Table 3, determining
theoretical equivalent widths using the line list in Table 2, and then
varying the model atmosphere parameters Teff, log(g), [Fe/H], and vt
individually while holding the other parameters fixed. We selected
parameter changes of 100K in Teff, 0.30dex in log(g), 0.15dex in [M/H],
and 0.30km/s in vt, which are reasonable when comparing our derived
parameters with those of the independent analysis by Zoccali et al. 2008
(cat. J/A+A/486/177; see also Section 3.1).
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Field Galactic bulge field
13- 20 A8 --- OGLE OGLE identification value (G2)
22- 25 F4.2 [Sun] sO ? 1σ line-to-line dispersion value for O (6)
27- 30 F4.2 [Sun] sNa ? 1σ line-to-line dispersion value for Na (6)
32- 35 F4.2 [Sun] sMg ? 1σ line-to-line dispersion value for Mg (6)
37- 40 F4.2 [Sun] sAl ? 1σ line-to-line dispersion value for Al (6)
42- 45 F4.2 [Sun] sSi 1σ line-to-line dispersion value for Si (6)
47- 50 F4.2 [Sun] sCa 1σ line-to-line dispersion value for Ca (6)
52- 55 F4.2 [Sun] sCr ? 1σ line-to-line dispersion value for Cr (6)
57- 60 F4.2 [Sun] sFeI 1σ line-to-line dispersion value for FeI (6)
62- 65 F4.2 [Sun] sFeII ? FeII 1σ line-to-line dispersion value (6)
67- 70 F4.2 [Sun] sCo ? 1σ line-to-line dispersion value for Co (6)
72- 75 F4.2 [Sun] sNi 1σ line-to-line dispersion value for Ni (6)
77- 80 F4.2 [Sun] sCu ? 1σ line-to-line dispersion value for Cu (6)
--------------------------------------------------------------------------------
Note (6): These values should be mostly representative of the combined
measurement error that includes effects such as continuum placement, line
deblending, synthesis fits via visual inspection, log(gf) uncertainties,
and model atmosphere deficiencies. For cases where only one line was
measured we have assigned a default value of 0.08. This is the average
dispersion value for all species in which more than one line was measured.
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Global notes:
Note (G1): Here we measure abundances of the Fe-peak elements Cr, Fe, Co, Ni,
and Cu, in addition to the light odd-Z and α-elements O, Na, Mg, Al,
Si, and Ca, in 156 red giant branch (RGB) stars in two Galactic bulge
fields at (l,b)=(+5.25,-3.02), and (l,b)=(0,-12). We note that the
(+5.25,-3.02) field also includes the bulge globular cluster NGC 6553.
Note (G2): These are the OGLE identification values given in the image headers,
and are also listed in Zoccali et al. 2008 (cat. J/A+A/486/177) and
Gonzalez et al. 2011 (cat. J/A+A/530/A54).
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 05-Jan-2015