While protoplanetary disks often appear to be compact and well-organized in millimeter continuum emission, CO spectral line observations are increasingly revealing complex behavior at large distances from the host star. We present deep ALMA maps of the $J=2-1$ transition of $^{12}$CO, $^{13}$CO, and C$^{18}$O, as well as the $J=3-2$ transition of DCO$^+$, toward the T Tauri star RU Lup at a resolution of $\sim0.3''$ ($\sim50$ au). The CO isotopologue emission traces four major components of the RU Lup system: a compact Keplerian disk with a radius of $\sim120$ au, a non-Keplerian ``envelope-like'' structure surrounding the disk and extending to $\sim260$ au from the star, at least five blueshifted spiral arms stretching up to 1000 au, and clumps outside the spiral arms located up to 1500 au in projection from RU Lup. We comment on potential explanations for RU Lup's peculiar gas morphology, including gravitational instability, accretion of material onto the disk, or perturbation by another star. RU Lup's extended non-Keplerian CO emission, elevated stellar accretion rate, and unusual photometric variability suggest that it could be a scaled-down Class II analog of the outbursting FU Ori systems.

中文翻译：

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与 T Tauri Star RU Lup 相关的大型 CO 螺旋臂和复杂运动学

虽然原行星盘在毫米连续谱发射中通常看起来很紧凑且组织良好，但 CO 谱线观测越来越多地揭示了远离主星的复杂行为。我们展示了 $^{12}$CO、$^{13}$CO 和 C$^{18}$O 的 $J=2-1$ 过渡的深度 ALMA 映射，以及 $J=3 -2$ DCO$^+$ 向 T Tauri 星 RU Lup 的过渡，分辨率为 $\sim0.3''$ ($\sim50$ au)。CO同位素体排放追踪RU Lup系统的四个主要组成部分：一个半径为$\sim120$ au的紧凑开普勒圆盘，一个围绕圆盘并延伸至$\sim260$的非开普勒“信封状”结构来自恒星的 au，至少有五个蓝移旋臂延伸至 1000 au，并且在 RU Lup 投影中位于 1500 au 的旋臂外有团块。我们评论了对 RU Lup 特殊气体形态的潜在解释，包括引力不稳定性、物质在圆盘上的吸积或另一颗恒星的扰动。RU Lup 扩展的非开普勒式 CO 排放、增加的恒星吸积率和不寻常的光度变化表明它可能是爆发的 FU Ori 系统的 II 类类似物。