J/A+A/580/A129 Sulphur in the Sculptor dSph (Skuladottir+, 2015)
Sulphur in the Sculptor dwarf spheroidal galaxy. Including NLTE corrections.
Skuladottir A., Andrievsky S.M., Tolstoy E., Hill V., Salvadori S.,
Korotin S.A., Pettini M.
<Astron. Astrophys., 580, A129-129 (2015)>
=2015A&A...580A.129S 2015A&A...580A.129S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Abundances
Keywords: stars: abundances - galaxies: abundances - galaxies: evolution -
galaxies: individual: Sculptor dwarf spheroidal - galaxies: dwarf
Abstract:
In Galactic halo stars, sulphur has been shown to behave like other
α-elements, but until now, no comprehensive studies have been
done on this element in stars of other galaxies. Here, we use
high-resolution ESO VLT/FLAMES/GIRAFFE spectra to determine sulphur
abundances for 85 stars in the Sculptor dwarf spheroidal galaxy,
covering the metallicity range -2.5≤[Fe/H]≤-0.8. The abundances are
derived from the SI triplet at 9213, 9228, and 9238Å. These lines
have been shown to be sensitive to departure from local thermodynamic
equilibrium, i.e. NLTE effects. Therefore, we present new NLTE
corrections for a grid of stellar parameters covering those of the
target stars. The NLTE-corrected sulphur abundances in Sculptor show
the same behaviour as other α-elements in that galaxy (such as
Mg, Si, and Ca). At lower metallicities ([Fe/H]≲-2) the abundances
are consistent with a plateau at [S/Fe]≃+0.16, similar to what is
observed in the Galactic halo, [S/Fe]≃+0.2. With increasing [Fe/H],
the [S/Fe] ratio declines, reaching negative values at [Fe/H]>-1.5.
The sample also shows an increase in [S/Mg] with [Fe/H], most probably
because of enrichment from Type Ia supernovae.
Description:
From the DART survey (Tolstoy et al., 2006Msngr.123...33T 2006Msngr.123...33T), detailed
abundance measurements are known for ∼100 stars spread over a 25'
diameter field of view in the Sculptor dSph (Tolstoy et al.,
2009ARA&A..47..371T 2009ARA&A..47..371T; Hill et al., in prep.). Because of the distance to
Sculptor, only the brightest stars are available for HR spectroscopy.
This sample, therefore, consists of relatively cool red giant branch
(RGB) stars, with Teff≲4700K. For an overlapping sample of 86 stars
in Sculptor, ESO VLT/GIRAFFE spectroscopy was carried out to measure
sulphur.
The observations presented here were taken in service mode in July and
August of 2012, all using the HR22B grating, which covers the
wavelength range 8960-9420Å th resolution R∼19000 .
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 117 86 Positions and stellar parameters of the target
stars in Sculptor, with Fe, Mg, and S abundance
measurements, including NLTE corrections for S
tablea2.dat 54 86 Abundances for individual sulphur lines with their
associated measurement errors and NLTE corrections
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See also:
J/A+A/574/A129 : The First CEMP star in the Sculptor dSph (Skuladottir+, 2015)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Star Star name (ETNNNN)
9 I1 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 18 F5.2 s RAs Right ascension (J2000)
20 A1 --- DE- declination sign (J2000)
21- 22 I2 deg DEd declination (J2000)
24- 25 I2 arcmin DEm declination (J2000)
27- 30 F4.1 arcsec DEs declination (J2000)
32- 35 I4 K Teff Effective temperature
37- 40 F4.2 [cm/s2] logg Surface gravity
42- 45 F4.2 km/s vt Trubulence velocity
46- 51 F6.1 km/s RV Radial velocity
53- 55 I3 --- S/N Signal-to-noise ratio
57- 61 F5.2 [-] [Fe/H] Metallicity
63- 66 F4.2 [-] e_[Fe/H] rms uncertainty on [Fe/H]
68- 72 F5.2 [-] [Mg/H] ?=- Abundance [Mg/H]
74- 77 F4.2 [-] e_[Mg/H] ?=- rms uncertainty on [Mg/H]
79 I1 --- NS Number of spectra
81- 84 F4.2 [-] logeps(S) Sulfur abundance (LTE)
86- 89 F4.2 --- dnoise Final error of the line
91- 95 F5.2 --- DNLTE NLTE correction
97-101 F5.2 [-] [S/Fe] Abundance [S/Fe] (NLTE)
103-106 F4.2 [-] e_[S/Fe] rms uncertainty on [S/Fe]
108-112 F5.2 [-] [S/Mg] ?=- Abundance [S/Mg] (NLTE)
114-117 F4.2 [-] e_[S/Mg] ?=- rms uncertainty on [S/Mg]
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Star Star name
8- 11 F4.2 --- logeps(S)1 First line (9213Å) sulfur abundance
13- 16 F4.2 --- dnoise1 First line (9213Å) final error
18- 22 F5.2 --- DNLTE1 First line (9213Å) NLTE correction
24- 27 F4.2 --- logeps(S)2 Second line (9213Å) sulfur abundance
29- 32 F4.2 --- dnoise2 Second line (9228Å) final error
34- 38 F5.2 --- DNLTE2 Second line (9228Å) NLTE correction
40- 43 F4.2 --- logeps(S)3 ?=- Third line (9238Å) sulfur abundance
45- 48 F4.2 --- dnoise3 ?=- Third line (9238Å) final error
50- 54 F5.2 --- DNLTE3 ?=- Third line (9238Å) NLTE correction
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 03-Nov-2015