Monte Carlo photoionization simulations of diffuse ionized gas
Monte Carlo photoionization simulations of diffuse ionized gas
复制标题
扩散电离气体的蒙特卡罗光电离模拟
DOI：
10.1111/j.1365-2966.2004.07846.x
复制
发表时间：
2004
影响因子：
4.8
通讯作者：
J. Mathis
中科院分区：
文献类型：
--
作者：
K. Wood;J. Mathis
我们表明，在银河系和其他星系中的弥漫电离气体（DIG）中，观察到的一些星云线比随中平面以上的高度的增加是辐射场远离中平面电离源逐渐硬化的自然结果。为了获得增加的温度和线比远离中平面，我们的多组分星际介质的光电离模拟不需要像以前的研究，采用一维，球平均模型的额外加热（超过和以上的光电离）。辐射泄漏到DIG从密度有界的H II区域一般是更难的H-电离连续体，并抑制其氦电离光子相比，H II区域的电离源。在与其他最近的调查，我们发现，这种泄漏H II区模型可以提供升高的温度和线比，和较低的He +馏分中的DIG。对于一个复合模型代表的相对光谱类型的O星在太阳附近，我们发现，自然硬化的辐射场达到大的高度，在我们的模拟可以解释大多数观察到的线比。然而，需要额外的加热来再现DIG中的最大线比率。Ke yw ords：Radiative transfer ‐ H II regions.
We demonstrate that the observed increase of some nebular line ratios with height above the midplane in the diffuse ionized gas (DIG) in the Milky Way and other galaxies is a natural consequence of the progressive hardening of the radiation field far from the midplane ionizing sources. To obtain increasing temperatures and line ratios away from the midplane, our photoionization simulations of a multicomponent interstellar medium do not require as much additional heating (over and above that from photoionization) as previous studies that employed one-dimensional, spherically averaged models. Radiation leaking into the DIG from density bounded H II regions is generally harder in the H-ionizing continuum and has its He-ionizing photons suppressed compared to the ionizing source of the H II region. In line with other recent investigations, we find that such leaky H II region models can provide elevated temperatures and line ratios, and a lower He + fraction in the DIG. For a composite model representing the relative spectral types of O stars in the solar neighbourhood, we find that the natural hardening of the radiation field reaching large heights in our simulations can explain most of the observed line ratios. However, additional heating is required to reproduce the largest line ratios in the DIG. Ke yw ords: radiative transfer ‐ H II regions.