WFPC2 Images of a Face-on Disk Surrounding TW Hydrae
WFPC2 Images of a Face-on Disk Surrounding TW Hydrae
复制标题
TW Hydrae 周围的面盘的 WFPC2 图像
DOI：
10.1086/309170
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
C. Burrows
中科院分区：
文献类型：
--
作者：
J. Krist;K. Stapelfeldt;F. Ménard;D. Padgett;C. Burrows
哈勃太空望远镜对孤立的金牛座T星星长蛇座TW的观测揭示了一个紧凑的星周星云的存在。在减去参考点扩散函数（PSF）后，在R和I波段WFPC 2图像中都可以看到平滑、对称的圆形光晕。它的强度随半径的增加而下降，直到达到3.5 ″（10200 Au）的外灵敏度极限。数值实验表明，PSF相减伪影不能解释光晕的亮度分布。相反，最可能的解释是光环是一个正面的星周盘。晕的径向亮度分布是复杂的，可以用多个连续的区域来描述，这些区域具有单独的幂律强度关系。相对于星星，光晕看起来略呈蓝色，特别是在外围区域。我们比较TW Hya晕单散射模型的面上的磁盘与多个径向区域。虽然具有垂直光学厚度τ v <$10 - 2的光学薄盘模型可以再现星云和恒星的相对亮度，但我们发现这样的模型具有较大的中面光学厚度，因此不是自洽的。我们提出了一个光学厚盘模型，匹配的径向亮度轮廓自洽，并有一个尘埃质量接近亚毫米连续测量所暗示的。在圆盘中发现的带状结构可能是由尘埃性质的径向变化引起的，这些尘埃性质决定了局部平衡温度，或者可能是通过看不见的同伴的动力学效应。
Hubble Space Telescope observations of the isolated T Tauri star TW Hydrae reveal the presence of a compact circumstellar nebula. After subtraction of a reference point-spread function (PSF), a smooth, symmetrical, circular halo can be seen in both R- and I-band WFPC2 images. Its intensity declines with radius until reaching an outer sensitivity limit at 3.″5 (≈200 AU). Numerical experiments show that PSF subtraction artifacts cannot account for the halo's brightness distribution. Instead, the most likely explanation is that the halo is a face-on circumstellar disk. The radial brightness profile of the halo is complex and can be described with multiple, contiguous zones with individual power-law intensity relations. The halo appears slightly blue relative to the star, especially in the outer zones. We compare the TW Hya halo to single-scattering models of face-on disks with multiple radial zones. While optically thin disk models with vertical optical depth τv ≈ 10-2 can reproduce the relative brightness of the nebula and star, we find that such models have large midplane optical depths and are therefore not self-consistent. We present an optically thick disk model that matches the radial brightness profile self-consistently and has a dust mass close to that implied by submillimeter continuum measurements. The zonal structure found in the disk could arise from radial variations in the dust properties that determine the local equilibrium temperature or perhaps via dynamical effects of unseen companions.