标题： 氦再结合线作为丰度和温度问题的探针 显示英文标题

标题： Helium Recombination Lines as a Probe of Abundance and Temperature Problems

摘要： 本文提出了一种简化公式，用于通过He I 7281/6678线的通量比来确定行星状星云（PNe）的电子温度Te(He I)。在我们之前关于Te(He I)的研究（Zhang等，2005年），我们使用了Benjamin等（1999年）提供的He I线发射系数。在这里，我们检查了Porter等（2005年）提供的更近期原子数据的结果。结果显示良好的一致性，表明原子数据不确定性对最终Te(He I)的影响可以忽略不计。我们还提出了一个分析公式，利用3421 Å的He I不连续性来推导电子温度。我们的分析表明，Te(He I)值显著低于从H I再结合光谱的巴耳末跃迁推导出的电子温度Te(H I)，以及从碰撞激发[O III]星云到晕线的禁线通量比推导出的Te([O III])。此外，Te(H I)的范围比Te(He I)或Te([O III])更广。这支持了双丰度星云模型，其中氢缺乏物质嵌入在“正常”化学成分（即接近太阳）的弥散气体中。 显示英文摘要

摘要： The paper presents a simplified formula to determine an electron temperature, Te(He I), for planetary nebulae (PNe) using the He I 7281/6678 line flux ratio. In our previous studies of Te(He I) (Zhang et al. 2005), we used the He I line emission coefficients given by Benjamin et al. (1999). Here we examine the results of using more recent atomic data presented by Porter et al. (2005). A good agreement is shown, suggesting that the effect of uncertainties of atomic data on the resultant Te(He I) is negligible. We also present an analytical formula to derive electron temperature using the He I discontinuity at 3421 A. Our analysis shows that Te(He I) values are significantly lower than electron temperatures deduced from the Balmer jump of H I recombination spectra, Te(H I), and that inferred from the collisionally excited [O III] nebular-to-auroral forbidden line flux ratio, Te([O III]). In addition, Te(H I) covers a wider range of values than either Te(He I) or Te([O III]). This supports the two-abundance nebular model with hydrogen-deficient material embedded in diffuse gas of a ``normal'' chemical composition (i.e. ~solar).