2015A&A...577A..18K


Query : 2015A&A...577A..18K

2015A&A...577A..18K - Astronomy and Astrophysics, volume 577A, 18-18 (2015/5-1)

Galactic evolution of sulphur as traced by globular clusters.

KACHAROV N., KOCH A., CAFFAU E. and SBORDONE L.

Abstract (from CDS):

Sulphur is an important volatile α element, but its role in the Galactic chemical evolution is still uncertain, and more observations constraining the sulphur abundance in stellar photospheres are required. We derive the sulphur abundances in red giant branch (RGB) stars in three Galactic halo globular clusters (GC) that cover a wide metallicity range (-2.3<[Fe/H]←1.2): M4 (NGC6121), M22 (NGC6656), and M30 (NGC7099). 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 α elements show star-to-star variations within individual GCs, and it is as yet unclear whether the α element sulphur also varies between GC stars. We used the infrared spectrograph CRIRES to obtain high-resolution (R∼50000), high signal-to-noise (S/N∼200 per px) spectra in the region of the SI multiplet 3 at 1045nm for 15 GC stars selected from the literature (six stars in M4, six stars in M22, and three 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]LTE=0.58±0.01±0.20dex (statistical and systematic error) for M4, [S/Fe]LTE=0.57±0.01±0.19dex for M22, and [S/Fe]LTE=0.55±0.02±0.16dex for M30. The negative NLTE corrections are estimated to be in the order of the systematic uncertainties. We do not detect star-to-star variations of the S abundance in any of the observed GCs, with the possible exception of two individual stars, one in M22 and one in M30, which appear to be highly enriched in S. With the tentative exception of two stars with measured high S abundances, we conclude that sulphur behaves like a typical α 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.

Abstract Copyright:

Journal keyword(s): stars: abundances - Galaxy: halo - globular clusters: individual: M 4 - globular clusters: individual: M 22 - globular clusters: individual: M 30 - globular clusters: general

VizieR on-line data: <Available at CDS (J/A+A/577/A18): table1.dat sp/*>

CDS comments: Table 1 objects 200051 and 200061 are misprint for [MMP2009b] 51 and [MMP2009b] 61 in SIMBAD.

Simbad objects: 26

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Number of rows : 26
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3781 0
2 Cl Trumpler 5 OpC 06 36 30 +09 27.9           ~ 113 0
3 NGC 2477 OpC 07 52 11 -38 32.2   6.64 5.8     ~ 277 0
4 * 10 Leo SB* 09 37 12.6793421832 +06 50 08.960833176   6.050 5.009     K1III 90 0
5 NGC 5822 OpC 15 04 12 -54 22.0           ~ 197 0
6 2MASS J16231442-2636055 RG* 16 23 14.4181955592 -26 36 05.547999564 14.64 12.73 10.88 9.80 9.04 ~ 43 0
7 NGC 6121 471 RG* 16 23 16.5623721744 -26 32 09.733929072 14.79 13.236 11.661   9.896 ~ 33 0
8 CD-26 11312 RG* 16 23 23.8093956576 -26 34 29.821786140 14.75 12.63 10.76   8.51 ~ 36 0
9 NGC 6121 45 RG* 16 23 29.1248946984 -26 30 29.805818400 14.92 13.354 11.781   9.988 ~ 43 0
10 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1784 0
11 2MASS J16233996-2628490 RG* 16 23 39.9822671376 -26 28 49.036544760 14.74 13.304 11.743   9.938 ~ 45 0
12 Cl* NGC 6121 MVP 27448 RG* 16 23 48.7977828528 -26 35 09.179191752   13.219 11.691   9.909 ~ 14 0
13 NGC 6397 GlC 17 40 42.09 -53 40 27.6     5.17     ~ 1911 0
14 NGC 6656 3052 * 18 36 10.1880699192 -23 54 22.149836316   13.2488 11.5217   9.6761 ~ 33 0
15 NGC 6656 3033 * 18 36 20.1391362096 -23 56 45.989405016   13.6269 12.2122   10.5598 ~ 14 0
16 M 22 GlC 18 36 23.94 -23 54 17.1           ~ 1320 0
17 NGC 6656 4020 * 18 36 25.9951256040 -23 55 58.727655408   13.6157 12.0413   10.3165 ~ 31 0
18 NGC 6656 1012 * 18 36 27.3693642144 -23 51 26.472598488   13.19 11.76   9.9282 ~ 26 0
19 NGC 6656 1086 * 18 36 32.1422845440 -23 51 31.749823080   13.7589 12.2961   10.6084 ~ 21 0
20 NGC 6656 4097 * 18 36 41.0626578168 -23 58 19.486392024   12.799 10.9295   8.9453 ~ 37 0
21 NGC 6752 GlC 19 10 52.11 -59 59 04.4           ~ 1927 0
22 Cl Terzan 7 GlC 19 17 43.92 -34 39 27.8           ~ 407 0
23 2MASS J21400211-2313002 RG* 21 40 02.1195489984 -23 13 00.159487572   14.071 12.972 12.833   ~ 5 0
24 2MASS J21401804-2310261 RG* 21 40 18.0516984144 -23 10 26.158994256   13.719 12.551     ~ 4 0
25 2MASS J21402180-2310090 RG* 21 40 21.8034119280 -23 10 09.145342956   13.560 12.092     ~ 5 0
26 M 30 GlC 21 40 22.12 -23 10 47.5     7.10     ~ 998 0

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2023.02.01-06:23:25

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