Clues on the Galactic evolution of sulphur from star clusters

Abstract

(Abridged) The abundances of alpha-elements are a powerful diagnostic of the star formation history and chemical evolution of a galaxy. Sulphur, being moderately volatile, can be reliably measured in the interstellar medium (ISM) of damped Ly-alpha galaxies and extragalactic HII regions. Measurements in stars of different metallicity in our Galaxy can then be readily compared to the abundances in external galaxies. Such a comparison is not possible for Si or Ca that suffer depletion onto dust in the ISM. Furthermore, studying sulphur is interesting because it probes nucleosynthetic conditions that are very different from those of O or Mg. The measurements in star clusters are a reliable tracers of the Galactic evolution of sulphur. We find <A(S)>NLTE=6.11+/-0.04 for M 4, <A(S)>NLTE=7.17+/-0.02 for NGC 2477, and <A(S)>NLTE=7.13+/-0.06 for NGC 5822. For the only star studied in Trumpler 5 we find A(S)NLTE=6.43+/-0.03 and A(S)LTE=6.94+/-0.05. Our measurements show that, by and large, the S abundances in Galactic clusters trace reliably those in field stars. The only possible exception is Trumpler 5, for which the NLTE sulphur abundance implies an [S/Fe] ratio lower by roughly 0.4 dex than observed in field stars of comparable metallicity, even though its LTE sulphur abundance is in line with abundances of field stars. Moreover the LTE sulphur abundance is consistent only with the abundance of another alpha-element, Mg, in the same star, while the low NLTE value is consistent with Si and Ca. The S abundances in our sample of stars in clusters imply that the clusters are chemically homogeneous for S within 0.05 dex.

arXiv commentA&A in press

References in corpus (38)

• First stars V - Abundance patterns from C to Zn and supernova yields in the early Galaxy
• Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere
• The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters
• A library of high resolution synthetic stellar spectra from 300nm to 1.8 micron with solar and alpha-enhanced composition
• Star-to-Star Abundance Variations among Bright Giants in the Mildly Metal-Poor Globular Cluster M4
• The exotic chemical composition of the Sagittarius dwarf Spheroidal galaxy
• First stars XII. Abundances in extremely metal-poor turnoff stars,and comparison with the giants
• A non-LTE study of neutral and singly-ionized calcium in late-type stars
• The Role of Type Ia Supernovae in Chemical Evolution I: Lifetime of Type Ia Supernovae and Galactic Supernova Rates
• Sulphur and zinc abundances in Galactic halo stars revisited
• The Ital-FLAMES survey of the Sagittarius dwarf Spheroidal galaxy. I. Chemical abundances of bright RGB stars
• Sulphur and zinc abundances in Galactic stars and damped Lyman-alpha systems
• Non-LTE Line-Formation and Abundances of Sulfur and Zinc in F, G, and K Stars
• The Sgr dSph hosts a metal-rich population
• Non-LTE abundances of Mg and K in extremely metal-poor stars and the evolution of [O/Mg], [Na/Mg], [Al/Mg] and [K/Mg] in the Milky Way
• Lithium abundances for 185 main-sequence stars - Galactic evolution and stellar depletion of lithium
• C, S, Zn and Cu abundances in planet-harbouring stars
• The forbidden 1082 nm line of sulphur: the photospheric abundance of sulphur in the Sun and 3D effects
• Sulphur abundances in disk stars: a correlation with silicon
• High-resolution spectroscopy of RGB stars in the Sagittarius Streams. I. Radial velocities and chemical abundances
• Sulphur abundance in Galactic stars
• Lithium and sodium in the globular cluster M4. Detection of a Li-rich dwarf star: preservation or pollution?
• MyGIsFOS: an automated code for parameter determination and detailed abundance analysis in cool stars
• A grid of NLTE corrections for magnesium and calcium in late-type giant and supergiant stars: application to Gaia
• NLTE determination of the calcium abundance and 3D corrections in extremely metal-poor stars
• First Stars XIV. Sulfur abundances in extremely metal-poor (EMP) stars
• A super lithium-rich red-clump star in the open cluster Trumpler 5
• Statistical equilibrium of silicon in the atmospheres of metal-poor stars
• Automatic abundance analysis of high resolution spectra
• Old open clusters in the Sagittarius dSph tidal stream -- kith or kin?
• Exploring the [S/Fe] Behavior of Metal-Poor Stars with the S I 1.046 micron Lines
• Sulphur abundances in halo giants from the [S I] line at 1082 nm and the S I triplet around 1045 nm
• Sulphur abundances in halo stars from Multiplet 3 at 1045 nm
• A UBVI and uvbyCaHbeta Analysis of the Intermediate-Age Open Cluster, NGC 5822
• Sulphur abundances in Terzan 7
• Sulphur in the Globular Clusters 47 Tucanae and NGC 6752
• Sulphur in the metal poor globular cluster NGC 6397
• Behavior of [S/Fe] in Very Metal-Poor Stars from the S I 1.046 micron Lines Revisited

Cited by in corpus (9)

• On the metallicity of open clusters. III. Homogenised sample
• New insights on Ba over-abundance in open clusters. Evidence for the intermediate neutron-capture process at play?
• The Gaia-ESO Survey: Galactic evolution of sulphur and zinc
• The chemistry of the most metal-rich damped Lyman $\alpha$ systems at z$\sim 2$ II. Context with the Local Group
• The Chemical Compositions of Very Metal-Poor Stars HD 122563 and HD 140283; A View From the Infrared
• MINCE I. Presentation of the project and of the first year sample
• The Galactic evolution of sulphur as traced by globular clusters
• Sulfur abundances in three Galactic clusters: Ruprecht 106, Trumpler 5 and Trumpler 20
• Asteroseismic age constraints on the open cluster NGC 2477 using oscillating stars identified with TESS FFI