The Dielectric Function of "Astrodust", and Absorption and Scattering Cross Sections for Spheroids

The dielectric function for "Astrodust" grain material is
provided for different assumed values of the dust grain shape (spheroid
axis ratio) and porosity (vacuum fraction), and fraction of the
interstellar iron present as metallic inclusions. For each case, the
dielectric function is obtained by requiring that the grains reproduce the
observed infrared opacity, and match to a physically reasonable dielectric
function at 1 micron, and extending to X-ray energies. The derived
dielectric functions satisfy the Kramers-Kronig relations. Dielectric
functions are provided from 1 Angstrom to 5 cm (12.4 keV to 2.59e-5 eV).
For each dielectric function, we also calculate absorption and scattering
corss sections for spheroidal grains, for three orientations of the grain
relative to incident linearly-polarized light, for wavelengths from the
Lyman limit (0.0912 micron) to the microwave (4 cm), and grain
"effective radii" a_eff from 3.162A to 5.012 micron.

针对"Astrodust"尘埃颗粒材料的介电函数（dielectric function），本数据集提供了不同假设参数下的结果，涵盖尘埃颗粒形状（椭球轴比，spheroid axis ratio）、孔隙率（真空占比）以及以金属夹杂物形式存在的星际铁占比。针对每种参数组合，介电函数的推导需满足两项条件：其一，尘埃颗粒能够复现观测到的红外不透明度；其二，该介电函数在1微米波长处匹配物理合理的介电函数，并将适用范围延伸至X射线能区。所推导得到的介电函数满足克拉默斯-克勒尼希关系（Kramers-Kronig relations）。介电函数的覆盖范围为1埃至5厘米（对应能区为12.4千电子伏至2.59×10^-5电子伏）。针对每个介电函数，我们还针对椭球形颗粒，计算了其相对于入射线偏振光的三种取向下的吸收截面与散射截面；相关计算的波长范围覆盖莱曼极限（0.0912微米）至微波波段（4厘米），颗粒有效半径（effective radii）的取值范围为3.162埃至5.012微米。