论文标题
紫外线CII线作为行星星云中Kappa分布电子的诊断
The ultraviolet CII lines as a diagnostic of kappa-distributed electrons in planetary nebulae
论文作者
论文摘要
在近年来，在行星星云（PNE）研究中，已提出了非马克斯韦利亚$κ$电子能量分布（EED）来解决所谓的``电子温度和``电子温度'''电子温度和丰度差异问题''。因此，需要开发诊断工具以从观察结果确定PNE的EED。由高能水平引起的，来自PNE当前强度的紫外线（UV）发射线敏感地取决于EED的高能尾巴。在这项工作中，我们研究了使用\ ion {c} {2}] $λ$ 2326/\ ion {c} {2} $ 1335强度比作为eed偏离Maxwellian分布的偏差的可行性（如$κ$κ$ index所示）。我们使用麦克斯韦分解方法来得出\ ion {c} {2}的理论$κ$ - 基于碰撞激发的系数，然后计算\ ion {c} {c} {2} uv强度比作为$κ$ index的函数。我们分析了{\ it International Ultraviolet Explorer}获得的档案光谱，并测量了12个PNE的\ ion {C} {2} uv线的强度。通过比较观察到的线比和理论预测，我们可以推断出它们的$κ$值。通过Maxwellian-Eed假设，观察到的\ ion {C} {2}] $λ$ 2326/\ ion {C} {2} $λ$ 1335比率通常低于从观察到的光谱中预测的比率。可以用$κ$ EED来解释这种差异。我们的结果表明，$κ$值推断的范围从15到无穷大，表明与麦克斯韦分布有轻度或适度的偏差。但是，$κ$分布的电子不太可能在整个星云中存在。玩具模型表明，如果PN中约有约1--5％的自由电子具有$κ$ - 欧洲的$κ= 3 $，则足以说明观测值。
Non-Maxwellian $κ$ electron energy distributions (EEDs) have been proposed in recent years to resolve the so-called ``electron temperature and abundance discrepancy problem'' in the study of planetary nebulae (PNe). Thus the need to develop diagnostic tools to determine from observations the EED of PNe is raised. Arising from high energy levels, the ultraviolet (UV) emission lines from PNe present intensities that depend sensitively on the high-energy tail of the EED. In this work, we investigate the feasibility of using the \ion{C}{2}]$λ$2326/\ion{C}{2}$λ$1335 intensity ratios as a diagnostic of the deviation of the EED from the Maxwellian distribution (as represented by the $κ$ index). We use a Maxwellian decomposition approach to derive the theoretical $κ$-EED-based collisionally excited coefficients of \ion{C}{2}, and then compute the \ion{C}{2} UV intensity ratio as a function of the $κ$ index. We analyze the archival spectra acquired by the {\it International Ultraviolet Explorer} and measure the intensities of \ion{C}{2} UV lines from 12 PNe. By comparing the observed line ratios and the theoretical predictions, we can infer their $κ$ values. With the Maxwellian-EED hypothesis, the observed \ion{C}{2}]$λ$2326/\ion{C}{2}$λ$1335 ratios are found to be generally lower than those predicted from the observed optical spectra. This discrepancy can be explained in terms of the $κ$ EED. Our results show that the $κ$ values inferred range from 15 to infinity, suggesting a mild or modest deviation from the Maxwellian distribution. However, the $κ$-distributed electrons are unlikely to exist throughout the whole nebulae. A toy model shows that if just about 1--5 percent of the free electrons in a PN had a $κ$-EED as small as $κ=3$, it would be sufficient to account for the observations.
