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arXiv 1508.04443astro-ph.EP
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带有嵌入行星的引力不稳定盘中螺旋臂的散射光图像

Scattered light images of spiral arms in marginally gravitationally unstable discs with an embedded planet

A. Pohl, P. Pinilla, M. Benisty, S. Ataiee, A. Juhasz, C. P. Dullemond, R. Van Boekel, T. Henning

备注：
Accepted for publication in MNRAS; 13 pages, 8 figures
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摘要：

过渡盘在近红外的散射光图像通常显示出非轴对称结构的形式，除了其特征性的低不透明度的内部间隙区域的大开口的螺旋臂。我们研究了自引力盘，并研究了引力不稳定性对行星盘相互作用引起的螺旋臂形状和对比度的影响。二维非等温流体动力学模拟，包括粘性加热和冷却处方相结合的三维尘埃连续辐射转移模型直接比较的意见。我们发现，所产生的螺旋和周围的光盘在散射光之间的对比度是远高于压力标度的高度变化，即热扰动，比纯表面密度的变化。自重力效应抑制了任何涡旋模式，并倾向于减小行星引起的螺旋的张开角，使它们缠绕得更紧。如果圆盘的引力稳定性只有在托姆雷参数为1的情况下才能维持，那么嵌入的大质量行星（行星与恒星的质量比为$10^{-2}$）就可能引发圆盘外层的引力不稳定性。由这种不稳定性和行星发射的密度波所产生的螺旋可以重叠，从而在外盘中产生大规模的、更开放的螺旋臂。这些螺旋的对比度远高于现有望远镜的探测极限。

英文摘要：

Scattered light images of transition discs in the near-infrared often show non-axisymmetric structures in the form of wide-open spiral arms in addition to their characteristic low-opacity inner gap region. We study self-gravitating discs and investigate the influence of gravitational instability on the shape and contrast of spiral arms induced by planet-disc interactions. Two-dimensional non-isothermal hydrodynamical simulations including viscous heating and a cooling prescription are combined with three-dimensional dust continuum radiative transfer models for direct comparison to observations. We find that the resulting contrast between the spirals and the surrounding disc in scattered light is by far higher for pressure scale height variations, i.e. thermal perturbations, than for pure surface density variations. Self-gravity effects suppress any vortex modes and tend to reduce the opening angle of planet-induced spirals, making them more tightly wound. If the disc is only marginally gravitationally stable with a Toomre parameter around unity, an embedded massive planet (planet-to-star mass ratio of $10^{-2}$) can trigger gravitational instability in the outer disc. The spirals created by this instability and the density waves launched by the planet can overlap resulting in large-scale, more open spiral arms in the outer disc. The contrast of these spirals is well above the detection limit of current telescopes.

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