行星还是褐矮星？使用中红外干涉测量法从壁形状推断HD 100546中的伴随质量
Planet or Brown Dwarf? Inferring the Companion Mass in HD 100546 from the Wall Shape using Mid-Infrared Interferometry
摘要：
巨大的行星形成于原行星盘中，而这些盘仍然富含气体，并且可以通过它们雕刻出的环形间隙揭示它们的存在。HD 100546是一个富含气体的圆盘，其半径在1到13天文单位之间，可能被行星伴星或行星系清除。我们想确定在盘隙远端附近看不见的伴星的性质。我们在多个基线处使用中红外干涉法来约束间隙远端处的盘壁的曲率。我们使用2D流体动力学模拟嵌入式行星和褐矮星，以估计粘度的磁盘和质量的同伴接近磁盘壁。我们发现，在远端的间隙盘壁是不垂直的，但圆了的表面密度的梯度。这样的梯度可以在流体动力学模拟中再现，具有单个重同伴（>=30. 80 M_Jup），而圆盘的粘度至少为α >~ 5 × 10^-3。考虑到间隙打开后温度结构的变化，行星质量和盘粘性的下限降低到20 M Jup，α = 2 10^-3。在HD 100546的盘隙中塑造盘壁的天体很可能是一颗60（+20）（-40）M Jup的棕矮星，而盘的粘度估计至少为α = 2 10^-3。盘的粘性是从盘的形态估计行星质量的一个重要因素：更粘的盘需要更重的行星来打开一个同样深的间隙。
英文摘要：
Giant planets form in protoplanetary disks while these disks are still gas-rich, and can reveal their presence through the annular gaps they carve out. HD 100546 is a gas-rich disk with a wide gap between between a radius of ~1 and 13 AU, possibly cleared out by a planetary companion or planetary system. We want to identify the nature of the unseen companion near the far end of the disk gap. We use mid-infrared interferometry at multiple baselines to constrain the curvature of the disk wall at the far end of the gap. We use 2D hydrodynamical simulations of embedded planets and brown dwarfs to estimate viscosity of the disk and the mass of a companion close to the disk wall. We find that the disk wall at the far end of the gap is not vertical, but rounded-off by a gradient in the surface density. Such a gradient can be reproduced in hydrodynamical simulations with a single, heavy companion (>=30...80 M_Jup) while the disk has viscosity of at least α >~ 5 10^-3. Taking into account the changes in the temperature structure after gap opening reduces the lower limit on the planet mass and disk viscosity to 20 M_Jup and α = 2 10^-3. The object in the disk gap of HD 100546 that shapes the disk wall is most likely a 60(+20)(-40) M_Jup brown dwarf, while the disk viscosity is estimated to be at least α = 2 10^-3. The disk viscosity is an important factor in estimating planetary masses from disk morphologies: more viscous disks need heavier planets to open an equally deep gap.
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