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首页> 外文期刊>Astronomy and astrophysics >Three-dimensional non-LTE radiative transfer effects in Fe?i lines - II. Line formation in 3D radiation hydrodynamic simulations
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Three-dimensional non-LTE radiative transfer effects in Fe?i lines - II. Line formation in 3D radiation hydrodynamic simulations

机译：Fe？i线中的三维非LTE辐射传递效应-II。 3D辐射流体动力学模拟中的线形成

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Here we investigate the effects of horizontal radiative transfer (RT) in combination with non-local thermodynamic equilibrum (NLTE) on important diagnostic iron lines in a realistic atmosphere. Using a snapshot of a 3D radiation-hydrodynamic (HD) simulation and a multilevel iron atom, we computed widely used Fe?i line profiles at three different levels of approximation of the RT (3D NLTE, 1D NLTE, LTE). By comparing the resulting line profiles and the circumstances of their formation, we gain new insight into the importance of horizontal RT. We find that the influence of horizontal RT is of the same order of magnitude as that of NLTE, although spatially more localized. Also, depending on the temperature of the surroundings, horizontal RT is found to either weaken or strengthen spectral lines. Line depths and equivalent width may differ by up to 20% from the corresponding LTE value if 3D RT is applied. Residual intensity contrasts in LTE are found to be larger than those in 3D NLTE by up to a factor of two. When compared to 1D NLTE, we find that horizontal RT weakens the contrast by up to 30% almost independently of the angle of line of sight. While the center-to-limb variation (CLV) of the 1D and 3D NLTE contrasts have a similar form, the LTE contrast CLV shows a different run. Determination of temperatures by 1D NLTE inversions of spatially resolved observations may produce errors of up to 200 K if one neglects 3D RT. We find a linear correlation between the intensity difference of 1D and 3D NLTE and a simple estimate of the temperature in the horizontal environment of the line formation region. This correlation could be used to coarsely correct inversions done in 1D NLTE for some of the effects of horizontal RT. Horizontal RT is less important if one considers spatially averaged line profiles because local line strengthening and weakening occur with similar frequency in our HD atmosphere. Thus, the iron abundance is underestimated by 0.012 dex if calculated using 1D NLTE RT. Since effects of horizontal RT are greatest for spatially resolved quantities, the use of 3D RT is particularly important for interpreting high spatial resolution observations.
机译：在这里，我们研究了在实际环境中水平辐射传输（RT）与非局部热力学平衡（NLTE）结合对重要诊断铁管线的影响。使用3D辐射流体动力学（HD）模拟的快照和多级铁原子，我们在RT的三种不同近似水平（3D NLTE，1D NLTE，LTE）上计算了广泛使用的Fe？i线轮廓。通过比较所得的线轮廓及其形成的环境，我们对水平RT的重要性有了新的认识。我们发现水平RT的影响与NLTE的影响数量级相同，尽管在空间上更局限。另外，根据周围环境的温度，水平RT被发现会减弱或增强光谱线。如果应用了3D RT，则线深度和等效宽度可能与相应的LTE值相差最多20％。发现LTE中的残余强度对比度比3D NLTE中的残余强度对比度大两倍。与一维NLTE相比，我们发现水平RT几乎与视线角度无关，最多可将对比度降低30％。虽然1D和3D NLTE对比的中心到边缘的变化（CLV）具有相似的形式，但LTE对比CLV显示的是不同的行程。如果一个人忽略了3D RT，则通过对空间分辨的观测值进行一维NLTE反演来确定温度可能会产生高达200 K的误差。我们发现1D和3D NLTE的强度差与线形成区域水平环境中温度的简单估计之间存在线性关系。对于水平RT的某些影响，该相关可用于粗略校正一维NLTE中完成的反演。如果考虑空间平均线轮廓，则水平RT不太重要，因为局部线的增强和减弱在我们的高清大气中以相似的频率发生。因此，如果使用一维NLTE RT计算，铁的丰度低估了0.012 dex。由于水平RT的影响对于空间分辨的量最大，因此3D RT的使用对于解释高空间分辨率的观测尤其重要。

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