论文标题
TW Hydrae磁盘中的气体和防尘阴影
Gas and Dust Shadows in the TW Hydrae Disk
论文作者
论文摘要
我们提出了来自TW HYA周围原球门磁盘的CO J = 2-1排放的新观察结果。检测到240 au（4英寸）的排放，发现表现出高达180 au（3英寸）的20％的方位角变化，而磁盘的西侧比东方更明亮。这种不对称被解释为追踪先前在散射光中看到的阴影。在辩论等人的散射光中对尘埃阴影的多上观测的重新分析。 （2017年）表明，振荡运动将为尘埃阴影而不是轨道运动的时间演变提供更好的模型。两种模型都可以预测尘埃阴影与气体阴影之间的角度偏移量高达〜100度。我们将这种偏移归因于粉尘晶粒和气体分子可以交换热量的有限速率，这是由气体分子和灰尘晶粒之间的碰撞速率主导的，$ t _ {\ rm coll} $。派生的角偏移等同于碰撞的时间尺度，范围从几乎瞬时到$ t _ {\ rm coll} $ 〜10年，具体取决于直线或弯曲的灰尘阴影，如辩论报道的HST观察结果所示。 （2017年）被采用。 $ t _ {\ rm coll} $的推断范围与基于代表性气体密度，温度，气盘比和谷物尺寸的预测一致。这些结果代表第一次可以将经验约束放在$ t _ {\ rm coll} $上。
We present new observations of CO J=2-1 emission from the protoplanetary disk around TW Hya. Emission is detected out to 240 au (4") and found to exhibit azimuthal variations up to 20% beyond 180 au (3"), with the west side of the disk brighter than the east. This asymmetry is interpreted as tracing the shadow previously seen in scattered light. A reanalysis of the multi-epoch observations of the dust shadow in scattered light from Debes et al. (2017) suggests that an oscillatory motion would provide a better model of the temporal evolution of the dust shadow rather than orbital motion. Both models predict an angular offset between the dust shadow and the gas shadow of up to ~100 deg. We attribute this offset to the finite rate at which dust grains and gas molecules can exchange heat, dominated by the collisional rate between gas molecules and dust grains, $t_{\rm coll}$. The angular offsets derived are equivalent to collisional timescales that range from the near instantaneous up to $t_{\rm coll}$ ~ 10 years, depending on whether a straight or a curved dust shadow, as suggested by HST observations reported by Debes et al. (2017), is adopted. The inferred range of $t_{\rm coll}$ are consistent with those predictions based on representative gas densities, temperatures, gas-to-dust ratios and grain sizes. These results represent the first time empirical constraints can be placed on $t_{\rm coll}$.
