J/A+A/577/A18 Reduced CRIRES spectra around S multiplet 3 (Kacharov+, 2015)
Galactic evolution of sulphur as traced by globular clusters.
Kacharov N., Koch A., Caffau E., Sbordone L.
<Astron. Astrophys. 577, A18 (2015)>
=2015A&A...577A..18K 2015A&A...577A..18K
ADC_Keywords: Clusters, globular ; Milky Way ; Spectra, infrared ; Abundances
Keywords: stars: abundances - Galaxy: halo -
globular clusters: individual: M4 -
globular clusters: individual: M22 -
globular clusters: individual: M30 - globular clusters: general
Abstract:
Sulphur is an important, volatile alpha element but its role in the
Galactic chemical evolution is still uncertain. We derive the S
abundances in RGB stars in three Galactic globular clusters (GC) that
cover a wide metallicity range (-2.3<[Fe/H]←1.2): M4, M22, and M30.
The halo field stars show a large scatter in the [S/Fe] ratio in this
metallicity span, which is inconsistent with canonical chemical
evolution models. To date, very few measurements of [S/Fe] exist for
stars in GCs, which are good tracers of the chemical enrichment of
their environment. However, some light and alpha elements show
star-to-star variations within individual GCs and it is yet unclear
whether sulphur also varies between GC stars. We used the the infrared
spectrograph CRIRES to obtain high-resolution (R∼50000), high
signal-to-noise (SNR∼200 per px) spectra in the region of the SI
multiplet 3 at 1045nm for 15 GC stars selected from the literature
(6 stars in M4, 6 stars in M22 and 3 stars in M30). Multiplet 3 is
better suited for S abundance derivation than the more commonly used
lines of multiplet 1 at 920nm, since its lines are not blended by
telluric absorption or other stellar features at low metallicity. We
used spectral synthesis to derive the [S/Fe] ratio of the stars
assuming local thermodynamic equilibrium (LTE). We find mean
[S/Fe]=0.58±0.01±0.20dex (statistical and systematic error) for
M4, [S/Fe]=0.57±0.01±0.19dex for M22, and
[S/Fe]=0.55±0.02±0.16dex for M30. The negative NLTE corrections
are estimated to be in the order of the systematic uncertainties. With
the tentative exception of two stars with measured high S abundances,
we conclude that sulphur behaves like a typical alpha element in the
studied Galactic GCs, showing enhanced abundances with respect to the
solar value at metallicities below [Fe/H]=-1.0dex without a
considerable spread.
Description:
We provide the reduced CRIRES spectra in the region of the S multiplet
3 for all 15 analysed stars together with the best fit synthetic
spectra. We have interpolated the Kurucz AODFNEW alpha-enhanced models
to produce the synthetic spectra with scaled solar input abundances
except the alpha elements, where [alpha/Fe]=0.4dex. The parameters
for the synthesis are provided in Table 1 of the article.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 132 15 Atmospheric parameters and [S/Fe] ratios of
the targeted stars
sp/* . 15 Individual spectra
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See also:
J/A+A/490/625 : Abundances of NGC 6121 red giants (Marino+, 2008)
J/A+A/505/139 : Red giants abundances in 17 globular clusters (Carretta+, 2009)
J/A+A/505/117 : Red giants abundances in 15 globular clusters (Carretta+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Cluster Globular cluster name (1)
5- 10 I6 --- ID Star identification number within the cluster
12- 15 I4 K Teff [3860/4500] Effective temperature
17- 20 F4.2 [cm/s2] logg [0.05/1.67] Surface gravity
22- 25 F4.2 km/s vtmic [1.5/2.4] Microturbulent velocity ξ
27- 31 F5.2 [Sun] [Fe/H] [-2.4/-1] Metallicity
33- 37 F5.2 [Sun] [Na/Fe] [-0.2/0.8] Na abundance
39- 42 F4.2 [Sun] e_[Na/Fe] [0.02/0.07] rms uncertainty on [Na/Fe]
44- 48 F5.2 [Sun] [O/Fe] [-0.3/0.51] O abundance
50- 53 F4.2 [Sun] e_[O/Fe] [0.04/0.2] rms uncertainty on [O/Fe]
55- 58 F4.2 [Sun] [Mg/Fe] [0.2/0.55]?=- Mg abundance
60- 63 F4.2 [Sun] e_[Mg/Fe] [0.04/0.2]? rms uncertainty on [Mg/Fe]
65- 68 F4.2 [Sun] [Ca/Fe] [0.16/0.42]?=- Ca abundance
70- 73 F4.2 [Sun] e_[Ca/Fe] [0.02/0.03]? rms uncertainty on [Ca/Fe]
75- 78 F4.1 km/s Vtmac [4.8/12.2] Macroturbulent velocity (2)
80- 82 F3.1 km/s e_Vtmac [0.1/0.9] rms uncertainty on Vtmac
84- 87 F4.2 [Sun] [S/Fe] [0.5/0.9] LTE S abundance (3)
89- 92 F4.2 [Sun] e_[S/Fe] [0.01/0.04] rms uncertainty on [S/Fe]
94-117 A24 --- SName Simbad name
119-132 A14 --- FileName Name of the table with spectrum in
subdirectory sp
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Note (1): IDs, atmospheric parameters, and abundances from
* for M4: Marino et al. (2008A&A...490..625M 2008A&A...490..625M, Cat. J/A+A/490/625)
* for M22: Marino et al. (2009A&A...505.1099M 2009A&A...505.1099M)
(the ID numbers 200051 and 200061 were fixed at CDS into 51 and 61)
* for M30: Carretta et al. (2009A&A...505..139C 2009A&A...505..139C, Cat. J/A+A/505/139,
2009A&A...505..117C 2009A&A...505..117C, Cat. J/A+A/505/117)
Adopted solar values in the references:
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M4 M22 M30
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A(Fe) 7.48 7.48 7.54
A(Na) 6.32 6.31 6.21
A(O) 8.83 8.83 8.79
A(Mg) 7.55 7.54 7.43
A(Ca) 6.39 6.39 6.27
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Note (2): free parameter in the fitting procedure.
Note (3): the adopted solar values are
A(Fe)=7.50, A(S)=7.16 (Caffau et al. 2011, Sol. Phys. 268, 255).
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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2- 10 F9.3 0.1nm lambda Wavelength in Angstroms
13- 20 F8.6 --- Fobs Observed flux normalised to 1.
23- 30 F8.6 --- Fmod Synthetic flux
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Acknowledgements:
Nikolay Kacharov, n.kacharov(at)lsw.uni-heidelberg.de
(End) Nikolay Kacharov [LSW, Heidelberg], Patricia Vannier [CDS] 17-Mar-2015