Galactic chemical evolution of sulphur

Matrozis, E.; Ryde, Nils; Dupree, A. K.

doi:10.1051/0004-6361/201322317

Cited by 18 publications

(17 citation statements)

References 66 publications

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“…3 Matrozis et al (2013) [SI] 39 Takeda et al (2016) 6,8 239 (Prochaska et al 2000;Reddy et al 2003Reddy et al , 2006Bensby et al 2003Bensby et al , 2005Bensby et al , 2013Bensby et al , 2014Allende Prieto et al 2004), the Galactic halo (Primas et al 2000;Cayrel et al 2004;Nissen et al 2004;Nissen et al 2007;Bonifacio et al 2009), the bulge (Barbuy et al 2015) and nearby dwarf galaxies (Sbordone et al 2007;Venn et al 2012;Skúladóttir et al in preparation). This implies that zinc is not necessarily a good tracer of iron and that its nucleosynthetic origin is probably more complex than previously thought.…”

Section: Zincmentioning

confidence: 99%

TheGaia-ESO Survey: Galactic evolution of sulphur and zinc

Duffau

Caffau

Sbordone

et al. 2017

A&A

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Context. Due to their volatile nature, when sulphur and zinc are observed in external galaxies, their determined abundances represent the gas-phase abundances in the interstellar medium. This implies that they can be used as tracers of the chemical enrichment of matter in the Universe at high redshift. Comparable observations in stars are more difficult and, until recently, plagued by small number statistics. Aims. We wish to exploit the Gaia ESO Survey (GES) data to study the behaviour of sulphur and zinc abundances of a large number of Galactic stars, in a homogeneous way. Methods. By using the UVES spectra of the GES sample, we are able to assemble a sample of 1301 Galactic stars, including stars in open and globular clusters in which both sulphur and zinc were measured. Results. We confirm the results from the literature that sulphur behaves as an α-element. We find a large scatter in [Zn/Fe] ratios among giant stars around solar metallicity. The lower ratios are observed in giant stars at Galactocentric distances less than 7.5 kpc. No such effect is observed among dwarf stars, since they do not extend to that radius. Conclusions. Given the sample selection, giants and dwarfs are observed at different Galactic locations, and it is plausible, and compatible with simple calculations, that Zn-poor giants trace a younger population more polluted by SN Ia yields. It is necessary to extend observations in order to observe both giants and dwarfs at the same Galactic location. Further theoretical work on the evolution of zinc is also necessary.

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Section: Zincmentioning

confidence: 99%

TheGaia-ESO Survey: Galactic evolution of sulphur and zinc

Duffau

Caffau

Sbordone

et al. 2017

A&A

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“…This helps to understand the interplay between field stars and clusters. The second is that, as clearly pointed out by Matrozis et al (2013), the uncertainties in sulphur determinations are largely due to the uncertainty in atmospheric parameters. The study of cluster stars helps to place constraints on the atmospheric parameters from the position of the star in the HR diagram.…”

Section: Introductionmentioning

confidence: 98%

Clues on the Galactic evolution of sulphur from star clusters

Caffau

Monaco

Spite³

et al. 2014

A&A

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Context. The abundances of α-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-α galaxies and extragalactic H ii 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. In this context measurements in star clusters are a reliable tracers of the Galactic evolution of sulphur. Aims. The aim of this paper is to determine sulphur abundances in several Galactic clusters that span a metallicity range −1.5 < [Fe/H] < 0.0. Methods. We use a standard abundance analysis, based on 1D model atmospheres in local thermodynamical equilibrium (LTE) and literature corrections for non-LTE (NLTE), as well as 3D corrections based on hydrodynamical model atmospheres, to derive sulphur abundances in a sample of stars in the globular cluster M 4, and the open clusters Trumpler 5, NGC 2477, and NGC 5822. Results. 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. Conclusions. 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 α-element, Mg, in the same star, while the low NLTE value is consistent with Si and Ca. We believe that further investigation of departures from LTE is necessary, as well as observation of other S i lines in this star and in other stars of the same cluster, before one can conclude that the sulphur abundance in Trumpler 5 is indeed 0.4 dex lower than in field stars of comparable metallicity. The S abundances in our sample of stars in clusters imply that the clusters are chemically homogeneous for S within 0.05 dex.

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“…Different studies report either a bimodality of the [S/Fe] ratio with a flat plateau and a branch of increasing abundance, reaching [S/Fe] ∼ 0.8 dex, or a plateau with a large scatter (see e.g. Nissen et al 2004Nissen et al , 2007Caffau et al 2005a;Spite et al 2011;Jönsson et al 2011;Matrozis et al 2013, and references therein).…”

Section: Introductionmentioning

confidence: 99%

“…It is interesting to find out whether a dichotomy or a large spread of the [S/Fe] ratio, as observed in the halo field stars, can also be found in GCs. The generally large uncertainties of the [S/Fe] measurements in the halo field stars are mostly driven by uncertainties of the atmospheric parameters (Matrozis et al 2013), and tracing the [S/Fe] ratio with GCs will therefore lead to more accurate results because of the much better constrained distances, gravities, and effective temperatures of GC stars from colourmagnitude diagrams (CMD). Additionally, our data will help to check if there are star-to-star variations of the S abundance in the different GCs and whether they correlate with the other α and light element abundances, such as O, Na, Si, Mg, and Al.…”

Section: Introductionmentioning

confidence: 99%

Galactic evolution of sulphur as traced by globular clusters

Kacharov

Koch

Caffau³

et al. 2015

A&A

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Context. 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. Aims. 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. 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. Methods. We used the infrared spectrograph CRIRES to obtain high-resolution (R ∼ 50 000), high signal-to-noise (S /N ∼ 200 per px) spectra in the region of the S I multiplet 3 at 1045 nm for 15 GC stars selected from the literature (six stars in M 4, six stars in M 22, and three stars in M 30). Multiplet 3 is better suited for S abundance derivation than the more commonly used lines of multiplet 1 at 920 nm, since its lines are not blended by telluric absorption or other stellar features at low metallicity. Results. 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 ± 0.20 dex (statistical and systematic error) for M 4, [S/Fe] LTE = 0.57 ± 0.01 ± 0.19 dex for M 22, and [S/Fe] LTE = 0.55 ± 0.02 ± 0.16 dex for M 30. 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 M 22 and one in M 30, which appear to be highly enriched in S. Conclusions. 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] − 1.0 dex without a considerable spread.

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Galactic chemical evolution of sulphur

Cited by 18 publications

References 66 publications

TheGaia-ESO Survey: Galactic evolution of sulphur and zinc

TheGaia-ESO Survey: Galactic evolution of sulphur and zinc

Clues on the Galactic evolution of sulphur from star clusters

Galactic evolution of sulphur as traced by globular clusters

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