论文标题
散射，温度梯度和沉降对观察到的原始磁盘的尘埃特性的影响
Effects of scattering, temperature gradients, and settling on the derived dust properties of observed protoplanetary disks
论文作者
论文摘要
众所周知，原星磁盘的毫米灰尘热发射受散射的影响，因此对于光学厚的磁盘，相对于纯吸收案例，发射降低，并且光谱指数可以达到低于2的值。后者也可以通过温度梯度获得。使用薄板中辐射转移的简单分析模型，我们量化了散射，垂直温度梯度以及尘埃沉淀在年轻恒星周围的几何薄面部积聚盘的发射和光谱指数上的效果。我们发现，在具有大型反照率（$ω_ν\ gtrsim 0.6 $）的垂直等温磁盘中，紧急强度可以在$ 10^{ - 2} $和$ 10^{ - 1} $之间的光学深度上增加。我们表明，由于磁盘发射主要追踪磁盘上层中的小尘土晶粒，因此灰尘沉降对光学厚度方向的光谱指数具有重要影响。当灰尘表面密度大于$ \ sim $ 3.21 g cm $^{ - 2} $时，这些小晶粒的$λ= 870 \μ$ m的排放可能会隐藏大谷物。最后，由于光谱能量分布的形状变化，光学厚度为1.3毫米，粒度在300 $ $ $ m $ <a _ {\ rm max} <$ 1毫米之间的谷物具有7 mm \ sim $ \ sim 60 $ \％，比从较高毫米频率中伸出的量度高于散射时的较高毫米频率。这种效果可以解释多个磁盘中报告的$λ= 7 $ mm的过剩排放。
It is known that the millimeter dust thermal emission of protoplanetary disks is affected by scattering, such that for optically thick disks the emission decreases with respect to the pure absorption case and the spectral indices can reach values below 2. The latter can also be obtained with temperature gradients. Using simple analytical models of radiative transfer in thin slabs, we quantify the effect of scattering, vertical temperature gradients, and dust settling on the emission and spectral indices of geometrically thin face-on accretion disks around young stars. We find that in vertically isothermal disks with large albedo ($ω_ν \gtrsim 0.6$), the emergent intensity can increase at optical depths between $10^{-2}$ and $10^{-1}$. We show that dust settling has important effects on the spectral indices in the optically thick regime, since the disk emission mainly traces small dust grains in the upper layers of the disk. The $λ= 870 \ μ$m emission of these small grains can hide large grains at the disk mid plane when the dust surface density is larger than $\sim$ 3.21 g cm$^{-2}$. Finally, because of the change of the shape of the spectral energy distribution, optically thick disks at 1.3 mm and grains with sizes between 300 $μ$m $< a_{\rm max} <$ 1 mm have a 7 mm flux $\sim 60$\% higher than the extrapolation from higher millimeter frequencies, assumed when scattering is neglected. This effect could provide an explanation to the excess emission at $λ= 7$ mm reported in several disks.
