A New Look at T Tauri Star Forbidden Lines: MHD-driven Winds from the Inner Disk
A New Look at T Tauri Star Forbidden Lines: MHD-driven Winds from the Inner Disk
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DOI：
10.3847/1538-4357/aae780
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发表时间：
2018-10
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通讯作者：
M. Fang;I. Pascucci;S. Edwards;U. Gorti;A. Banzatti;M. Flock;P. Hartigan;G. Herczeg;A. Dupree
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作者：
M. Fang;I. Pascucci;S. Edwards;U. Gorti;A. Banzatti;M. Flock;P. Hartigan;G. Herczeg;A. Dupree
磁流体动力学（MHD）和光蒸发风被认为在行星形成盘的演化和扩散中起着重要作用。我们报告了对48颗金牛座T星样本中[S ii] λ4068、[O i] λ5577和[O i] λ6300谱线的首次高分辨率（Δv <$6 km s−1）分析。按照Simon等人的方法，我们将其分解为三个运动学分量：与射流相关的高速分量（HVC），以及低速窄（LVC-NC）和宽（LVC-BC）分量。我们证实了以前的发现，许多LVC的蓝移超过1.5 km s-1，因此很可能是一种缓慢的盘风。我们进一步表明，个人组成部分的配置文件是类似的三条线。我们发现大多数LVC-NC和LVC-BC谱线比可以用温度在5000 ~ 10，000 K之间、电子密度在107-108 cm−3之间的热激发气体来解释。HVC比可以用激波前H数密度为106-107 cm−3的激波模型更好地再现。使用这些物理性质，我们估计的LVC和HVC。与以前的工作一致，在喷流中进行的质量是适度的吸积率相比。在可能假设LVC-NC风高度大于LVC-BC的情况下，发现LVC-BC高于LVC-NC。这些结果表明，大部分的质量损失发生在靠近中央星星，在几个Au，通过磁流体驱动的风。根据风的高度，MHD风可能在盘质量的演变中起主要作用。
Magnetohydrodynamic (MHD) and photoevaporative winds are thought to play an important role in the evolution and dispersal of planet-forming disks. We report the first high-resolution (Δv ∼ 6 km s−1) analysis of [S ii] λ4068, [O i] λ5577, and [O i] λ6300 lines from a sample of 48 T Tauri stars. Following Simon et al. we decompose them into three kinematic components: a high-velocity component (HVC) associated with jets, and low-velocity narrow (LVC-NC) and broad (LVC-BC) components. We confirm previous findings that many LVCs are blueshifted by more than 1.5 km s−1 and thus most likely trace a slow disk wind. We further show that the profiles of individual components are similar in the three lines. We find that most LVC-NC and LVC-BC line ratios are explained by thermally excited gas with temperatures between 5000 and 10,000 K and electron densities of ∼107–108 cm−3. The HVC ratios are better reproduced by shock models with a pre-shock H number density of ∼106–107 cm−3. Using these physical properties, we estimate for the LVC and for the HVC. In agreement with previous work, the mass carried out in jets is modest compared to the accretion rate. With the likely assumption that the LVC-NC wind height is larger than the LVC-BC, the LVC-BC is found to be higher than the LVC-NC. These results suggest that most of the mass loss occurs close to the central star, within a few au, through an MHD-driven wind. Depending on the wind height, MHD winds might play a major role in the evolution of the disk mass.