论文标题
星际灰尘的新分析散射相函数
A new analytical scattering phase function for interstellar dust
论文作者
论文摘要
上下文：通过星际灰尘晶粒对散射进行正确建模，需要对散射相函数进行良好的表征。 Henyey-Greenstein相位功能已成为描述尘埃颗粒各向异性散射的标准，但这是对光学范围之外的真实散射相函数的差分表示。目的：我们研究了Henyey-Greenstein相函数的替代方法，该功能将允许描述尘埃的散射特性。我们的目标是在现实主义和复杂性之间找到平衡：散射相功能应足够灵活，以便在宽波长范围内为防尘晶的散射特性提供准确的拟合，并且应该足够简单以易于处理，尤其是在辐射传输计算的背景下。方法：我们将各种分析相函数拟合到与Bare-Gr-S模型相对应的散射相函数，这是星际尘埃的最流行和通常采用的模型之一。我们权衡拟合的精度与分析相函数中的自由参数数量。结果：我们确认，Henyey-Greenstein相的功能很差描述了粉尘粒的散射，尤其是在紫外线（UV）波长下，相对差异高达50％。排水相函数在近红外（NIR）波长下减轻了此问题，但在紫外线中不能减轻该问题。最近在纳米级材料和水生介质的光散射的背景下提倡的两项雷诺 - 麦考密克相位功能很好地描述了裸-G-S数据，但其五个免费参数是退化的。我们提出了一个更简单的相位函数，即两项超球2（TTU2）相位函数，它在整个UV-NIR波长范围内也为裸-S-S相函数提供了极好的拟合。 （简略）
Context: Properly modelling scattering by interstellar dust grains requires a good characterisation of the scattering phase function. The Henyey-Greenstein phase function has become the standard for describing anisotropic scattering by dust grains, but it is a poor representation of the real scattering phase function outside the optical range. Aims: We investigate alternatives for the Henyey-Greenstein phase function that would allow the scattering properties of dust grains to be described. Our goal is to find a balance between realism and complexity: the scattering phase function should be flexible enough to provide an accurate fit to the scattering properties of dust grains over a wide wavelength range, and it should be simple enough to be easy to handle, especially in the context of radiative transfer calculations. Methods: We fit various analytical phase functions to the scattering phase function corresponding to the BARE-GR-S model, one of the most popular and commonly adopted models for interstellar dust. We weigh the accuracy of the fit against the number of free parameters in the analytical phase functions. Results: We confirm that the Henyey-Greenstein phase functions poorly describe scattering by dust grains, particularly at ultraviolet (UV) wavelengths, with relative differences of up to 50%. The Draine phase function alleviates this problem at near-infrared (NIR) wavelengths, but not in the UV. The two-term Reynolds-McCormick phase function, recently advocated in the context of light scattering in nanoscale materials and aquatic media, describes the BARE-GR-S data very well, but its five free parameters are degenerate. We propose a simpler phase function, the two-term ultraspherical-2 (TTU2) phase function, that also provides an excellent fit to the BARE-GR-S phase function over the entire UV-NIR wavelength range. (Abridged)
