The Chemical Composition of the Small Magellanic Cloud HiiRegion NGC 346 and the Primordial Helium Abundance
- 1 October 2000
- journal article
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 541 (2) , 688-700
- https://doi.org/10.1086/309485
Abstract
Spectrophotometry in the 3400-7400 range is presented for 13 areas of the brightest H II region in the SMC: NGC 346. The observations were obtained at CTIO with the 4-m telescope. Based on these observations its chemical composition is derived. The helium and oxygen abundances by mass are given by: Y(SMC)=0.2405+-0.0018 and O(SMC)=0.00171+-0.00025. From models and observations of irregular and blue compact galaxies it is found that dY/dO=3.5+-0.9 and consequently that the primordial helium abundance by mass is given by: Yp=0.2345+-0.0026 (1-sigma). This result is compared with values derived from Big Bang nucleosynthesis, and with other determinations of Yp.Comment: 32 pages + 5 figures Referee Revised VersioKeywords
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