飞碟的阴影：大尘埃颗粒的非常低的温度
The shadow of the Flying Saucer: A very low temperature for large dust grains
摘要：
尘埃决定了原行星盘的温度结构。然而，尘埃温度的测定几乎总是依赖于一个复杂的建模的光谱能量分布。我们试图直接测定发射毫米波长的大颗粒的温度。我们观察到的边缘尘埃盘的飞碟，出现在剪影对CO J=2-1发射从背景分子云在$ρ$ Oph。由于Keplerian旋转的磁盘和CO背景中的强度变化作为速度的函数的速度梯度的组合，使我们能够直接测量%吸收尘埃温度。尘埃的不透明度可以从发射的连续辐射中得到。尘埃盘以几种速度吸收来自CO云的辐射。我们得到非常低的尘埃温度，5至7 K在半径约100 AU，这是远远低于大多数模型的预测。尘埃光学厚度在230 GHz时为$> 0.2$，在100 au时的标度高度至少为8 au（最佳拟合值为13 au）。然而，灰尘盘非常平坦（张开指数-0.35），这表明灰尘沉降在外部。
英文摘要：
Dust determines the temperature structure of protoplanetary disks. However, dust temperature determinations almost invariably rely on a complex modeling of the Spectral Energy Distribution. We attempt a direct determination of the temperature of large grains emitting at mm wavelengths.} We observe the edge-on dust disk of the Flying Saucer, which appears in silhouette against the CO J=2-1 emission from a background molecular cloud in $ρ$ Oph. The combination of velocity gradients due to the Keplerian rotation of the disk and intensity variations in the CO background as a function of velocity allows us to directly measure the %absorbing dust temperature. The dust opacity can then be derived from the emitted continuum radiation. The dust disk absorbs the radiation from the CO clouds at several velocities. We derive very low dust temperatures, 5 to 7 K at radii around 100 au, which is much lower than most model predictions. The dust optical depth is $> 0.2$ at 230 GHz, and the scale height at 100 au is at least 8 au (best fit 13 au). However, the dust disk is very flat (flaring index -0.35), which is indicative of dust settling in the outer parts.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
