标题： 围绕吸积原行星的温暖气泡中CO的重现及其可观测性 显示英文标题

标题： Resurgence of CO in a warm bubble around accreting protoplanets and its observability

摘要： 原恒星盘的寒冷外区预计会包含一个位于中平面的层，气体中的CO分子在此冻结，其总体丰度较低。 该层在CO旋转发射线的通道图中表现为一个空洞。 我们探讨被冻结的层是否能将嵌入的吸积原行星的环绕环境暴露给观测。 为此，我们进行了3D辐射气体-尘埃流体动力学模拟，其消光由亚微米和毫米大小尘埃颗粒的再分布决定。 考虑了一个质量为木星的行星，其吸积光度为$\sim$$10^{-3}\,L_{\odot}$ 作为标准情况。 吸积加热在行星周围维持了一个温暖的气泡，局部增加了气体中CO分子的丰度。 出射天空图像的辐射转移预测表明，气泡在通道图中成为一个显著的CO发射源。 它表现为一个低强度的光学厚斑点，位于所谓的“蜻蜓翅膀”之间，这些“蜻蜓翅膀”追踪了前向和后向的线形成表面。 气泡的发射强度几乎与示踪同位素无关，这表明只要其信号能够从扩展的盘发射中分离出来，就会有非常丰富的可观测化学成分。 这可以通过在行星引起的间隙中光学薄或弱热分层的同位素实现，例如C$^{18}$O。 对于这些同位素，气泡在减去从盘动力学推导出的轴向平均通道图后的合成ALMA观测中突出显示为最亮的残差，从而实现了对形成中的原行星的新自动检测。 相比之下，马蹄形流动持续地从环绕行星环境中耗尽大尘埃颗粒，这使得该区域在亚毫米连续谱中不可观测，这与ALMA检测的稀缺性一致。 显示英文摘要

摘要： The cold outer regions of protoplanetary disks are expected to contain a midplane-centered layer where gas-phase CO molecules freeze out and their overall abundance is low. The layer then manifests itself as a void in the channel maps of CO rotational emission lines. We explore whether the frozen-out layer can expose the circumplanetary environment of embedded accreting protoplanets to observations. To this end, we performed 3D radiative gas-dust hydrodynamic simulations with opacities determined by the redistribution of submicron- and millimeter-sized dust grains. A Jupiter-mass planet with an accretion luminosity of $\sim$$10^{-3}\,L_{\odot}$ was considered as the nominal case. The accretion heating sustains a warm bubble around the planet, which locally increases the abundance of gas-phase CO molecules. Radiative transfer predictions of the emergent sky images show that the bubble becomes a conspicuous CO emission source in channel maps. It appears as a low-intensity optically thick spot located in between the so-called dragonfly wings that trace the fore- and backside line-forming surfaces. The emission intensity of the bubble is nearly independent of the tracing isotopolog, suggesting a very rich observable chemistry, as long as its signal can be deblended from the extended disk emission. This can be achieved with isotopologs that are optically thin or weakly thermally stratified across the planet-induced gap, such as C$^{18}$O. For these, the bubble stands out as the brightest residual in synthetic ALMA observations after subtraction of axially averaged channel maps inferred from the disk kinematics, enabling new automatic detections of forming protoplanets. By contrast, the horseshoe flow steadily depletes large dust grains from the circumplanetary environment, which becomes unobservable in the submillimeter continuum, in accordance with the scarcity of ALMA detections.