论文标题
氦气丰度及其径向梯度来自HII区域的光谱和银河系的戒指
Helium abundances and its radial gradient from the spectra of HII regions and ring nebulae of the Milky Way
论文作者
论文摘要
我们通过19 $ \ text {h} \ thinspace \ text {ii} $区域和围绕巨大的o恒星的环状阳离子从星系圆盘中确定氦圆盘的径向丰度梯度。 We revise the Galactocentric distances of the objects considering {\it Gaia} DR2 parallaxes and determine the physical conditions and the ionic abundance of He$^{+}$ in a homogeneous way, using between 3 and 10 $\text{He}\thinspace \text{I}$ recombination lines in each object.我们使用四个不同的ICF（HE）方案估计了星云的总丰度及其径向丰度梯度。梯度的斜率始终是负面的，并且微弱地依赖于ICF（HE）方案，尤其是当仅考虑具有log（$η$）$ <$ 0.9的对象时。斜率值从$ - $ 0.0078到$ - $ 0.0044 dex kpc $^{ - 1} $，与银河系化学进化模型的预测以及圆盘星系的化学动力学模拟的预测一致。最后，我们估计了银河WR恒星周围的环形星云样本中HE，O和N的丰度偏差，发现在三个Stellar Extela Ring Nebulae中，他的过度含量约为+0.24 $ \ pm $ 0.11 dex。
We determine the radial abundance gradient of helium in the disc of the Galaxy from published spectra of 19 $\text{H}\thinspace \text{II}$ regions and ring nebulae surrounding massive O stars. We revise the Galactocentric distances of the objects considering {\it Gaia} DR2 parallaxes and determine the physical conditions and the ionic abundance of He$^{+}$ in a homogeneous way, using between 3 and 10 $\text{He}\thinspace \text{I}$ recombination lines in each object. We estimate the total He abundance of the nebulae and its radial abundance gradient using four different ICF(He) schemes. The slope of the gradient is always negative and weakly dependent on the ICF(He) scheme, especially when only the objects with log($η$) $<$ 0.9 are considered. The slope values go from $-$0.0078 to $-$0.0044 dex kpc$^{-1}$, consistent with the predictions of chemical evolution models of the Milky Way and chemodynamical simulations of disc galaxies. Finally, we estimate the abundance deviations of He, O and N in a sample of ring nebulae around Galactic WR stars, finding a quite similar He overabundance of about +0.24 $\pm$ 0.11 dex in three stellar ejecta ring nebulae.
