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Hydrogen column density evaluations toward Capella: consequences on the interstellar deuterium abundance

机译:对Capella的氢气柱密度评估:对Capella的影响  星际氘丰度

摘要

The deuterium abundance evaluation in the direction of Capella has for a longtime been used as a reference for the local interstellar medium (ISM) withinour Galaxy. We show here that broad and weak HI components could be present onthe Capella line of sight, leading to a large new additional systematicuncertainty on the N(HI) evaluation. The D/H ratio toward Capella is found to be equal to 1.67 (+/-0.3)x10^-5 withalmost identical chi^2 for all the fits (this range includes only thesystematic error; the 2 sigma statistical one is almost negligible incomparison). It is concluded that D/H evaluations over HI column densitiesbelow 10^19 cm^-2 (even perhaps below 10^20 cm^-2 if demonstrated by additionalobservations) may present larger uncertainties than previously anticipated. Itis mentionned that the D/O ratio might be a better tracer for DI variations inthe ISM as recently measured by the Far Ultraviolet Spectroscopic Explorer(FUSE).
机译:长期以来,沿Capella方向进行的氘丰度评估一直被用作我们银河系中本地星际介质(ISM)的参考。我们在这里表明,Capella视线中可能存在宽泛且较弱的HI分量,从而导致N(HI)评估出现了新的较大的系统不确定性。发现对Capella的D / H比等于1.67(+/- 0.3)x10 ^ -5,并且所有拟合几乎相同,chi ^ 2(此范围仅包括系统误差; 2 sigma统计值几乎可以忽略不计)。结论是,HI柱密度在10 ^ 19 cm ^ -2以下(如果通过其他观察表明,甚至可能在10 ^ 20 cm ^ -2以下)的D / H评价可能会比以前预期的不确定性更大。据提到,D / O比可能是ISM中DI变化的更好示踪剂,最近由远紫外光谱浏览器(FUSE)测量。

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    Vidal-Madjar A.; Ferlet R.;

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  • 年度 2002
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