The helium abundance in the metal-poor globular clusters M30 and NGC6397
| Autor: | Francesco R. Ferraro, Alessio Mucciarelli, Barbara Lanzoni, L. Lovisi |
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| Přispěvatelé: | A. Mucciarelli, L. Lovisi, B. Lanzoni, F. R. Ferraro |
| Rok vydání: | 2014 |
| Předmět: |
chemistry.chemical_element
FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences Abundance (ecology) Galaxy: globular clusters: general 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Helium Astrophysics::Galaxy Astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Line (formation) Physics Very Large Telescope 010308 nuclear & particles physics Astronomy and Astrophysics Horizontal branch Stars Star cluster chemistry Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Globular cluster Astrophysics::Earth and Planetary Astrophysics |
| DOI: | 10.48550/arxiv.1403.0595 |
| Popis: | We present the helium abundance of the two metal-poor clusters M30 and NGC6397. Helium estimates have been obtained by using the high-resolution spectrograph FLAMES at the ESO Very Large Telescope and by measuring the HeI line at 4471 A in 24 and 35 horizontal branch stars in M30 and NGC6397, respectively. This sample represents the largest dataset of He abundances collected so far in metal-poor clusters. The He mass fraction turns out to be Y=0.252+-0.003 (sigma=0.021) for M30 and Y=0.241+-0.004 (sigma=0.023) NGC6397. These values are fully compatible with the cosmological abundance, thus suggesting that the horizontal branch stars are not strongly enriched in He. The small spread of the Y distributions are compatible with those expected from the observed main sequence splitting. Finally, we find an hint of a weak anticorrelation between Y and [O/Fe] in NGC6397 in agreement with the prediction that O-poor stars are formed by (He-enriched) gas polluted by the products of hot proton-capture reactions. Comment: Accepted for publication by ApJ |
| Databáze: | OpenAIRE |
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