论文标题
Lyα星云中的辐射转移：I。用中央源建模连续或块状球形光环
Radiative Transfer in Lyα Nebulae: I. Modeling a Continuous or Clumpy Spherical Halo with a Central Source
论文作者
论文摘要
为了了解高$ z $ ly $α$ nebulae背后的机制，我们模拟了$ \ rm h \，i $ halo在中央ly $α$源中的散射。 For the first time, we consider both smooth and clumpy distributions of halo gas, as well as a range of outflow speeds, total $\rm H\,I$ column densities, $\rm H\,I$ spatial concentrations, and central source galaxies (e.g., with Ly$α$ line widths corresponding to those typical of AGN or star-forming galaxies).我们计算原子氢分散的$ al $α$光子的偏振。我们的仅散射模型以总列密度$ n _ {\ rm hi} \ geq 10^{20} \ rm cm cm^{ - 2} $的典型大小（$ \ sim 100 \，$ kpc）的典型大小（$ \ sim 100 \，$ kpc）重现了总列密度$ n _ {\ rm hi} \ geq 10^{20} \ rm cm^{ - 2} $，并预测阳性，平面，平面和负极散热的范围。我们还发现了两个通用类别的$α$星云形态：有和没有明亮的核心。当$ n _ {\ rm hi} $很低时，即当中央源直接可见并且与极化跳跃相关联时，可以看到芯子，而偏光径向镜头却急剧增加。在我们平滑或块状媒体模型中测试的所有参数中，$ n _ {\ rm hi} $占据了趋势。 Ly $α$表面亮度，光谱线形状和块状模型中的极化的径向行为，覆盖因子$ f_c \ gtrsim 5 $接近相同$ n _ {\ rm hi} $的光滑模型的径向亮度。具有高$ n _ {\ rm hi} $和低$ f_c \ lyssim 2 $的块状介质，通过散射生成ly $α$的特征，光滑模型无法：明亮的核心，对称线条配置文件和极化跳跃。
To understand the mechanism behind high-$z$ Ly$α$ nebulae, we simulate the scattering of Ly$α$ in a $\rm H\,I$ halo about a central Ly$α$ source. For the first time, we consider both smooth and clumpy distributions of halo gas, as well as a range of outflow speeds, total $\rm H\,I$ column densities, $\rm H\,I$ spatial concentrations, and central source galaxies (e.g., with Ly$α$ line widths corresponding to those typical of AGN or star-forming galaxies). We compute the spatial-frequency diffusion and the polarization of the Ly$α$ photons scattered by atomic hydrogen. Our scattering-only model reproduces the typical size of Ly$α$ nebulae ($\sim 100\,$kpc) at total column densities $N_{\rm HI} \geq 10^{20} \rm cm^{-2}$ and predicts a range of positive, flat, and negative polarization radial gradients. We also find two general classes of Ly$α$ nebula morphologies: with and without bright cores. Cores are seen when $N_{\rm HI}$ is low, i.e., when the central source is directly visible, and are associated with a polarization jump, a steep increase in the polarization radial profile just outside the halo center. Of all the parameters tested in our smooth or clumpy medium model, $N_{\rm HI}$ dominates the trends. The radial behaviors of the Ly$α$ surface brightness, spectral line shape, and polarization in the clumpy model with covering factor $f_c \gtrsim 5$ approach those of the smooth model at the same $N_{\rm HI}$. A clumpy medium with high $N_{\rm HI}$ and low $f_c \lesssim 2$ generates Ly$α$ features via scattering that the smooth model cannot: a bright core, symmetric line profile, and polarization jump.
