Evolution of CO lines in time-dependent models of protostellar disk formation
Evolution of CO lines in time-dependent models of protostellar disk formation
复制标题
原恒星盘形成的时间依赖性模型中CO谱线的演化
DOI：
10.1051/0004-6361/201220885
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发表时间：
2013
影响因子：
6.5
通讯作者：
Cfa
中科院分区：
文献类型：
--
作者：
D. Harsono;R. Visser;S. Bruderer;E. Dishoeck;Lars E. Kristensen Leiden Observatory;Sron;U. Michigan;Mpe Garching;Cfa
上下文。恒星和行星形成理论预测，当包层坍塌并形成吸积盘时，密度、温度和速度结构将发生变化。虽然连续发射可以跟踪尘埃的演化，但需要光谱分辨的分子线来确定物理结构和坍塌动力学。目标。这项工作的目的是模拟低质量恒星形成过程中分子激发、谱线轮廓和相关可观测参数的演化。具体地说，研究了深嵌入阶段(Menv>；M�)磁盘的特征。方法：研究方法。Visser及其合作者的二维轴对称半解析模型被用来描述从前恒星到T-Tauri相的密度、恒星质量和光度的演化。为了准确确定随时间变化的尘埃温度，进行了全辐射传输计算。CO丰度随时间的变化由吸附和热脱附化学得到。CO的非LTE近红外(NIR)、远红外(FIR)和亚毫米线已经在多个时间步长处被模拟。结果。在单盘(10−20��束)中，通过高激发的13CO和C18O谱线最好地探测了崩塌过程中的动力学，这两条谱线被注入过程显著展宽。与尘埃温度相反，从亚mm/FIR数据得到的CO激发温度在原恒星演化过程中没有变化，这与用Herschel和地面望远镜获得的C18O观测结果一致。近红外光谱不仅探测寒冷的外包层，而且探测温暖的内区，为亚毫米谱线提供了补充信息。近红外高J(≥8)吸收线对内部少数AU的物理结构特别敏感，这确实显示出演化。模型表明，在≤1��(140pC)束流中观测13条CO和C18O1ow-J亚毫米谱线非常适合探测第I阶段(Menv<；M�)源中的嵌入盘，这与最近的干涉观测一致。需要使用ALMA的高信噪比亚角秒分辨率数据来在阶段0期间检测小型旋转支承磁盘的存在，并讨论各种诊断方法。将空间和光谱分辨谱线与ALMA和At NIR相结合，是探测嵌入相内包络和盘状结构形成过程的有力手段。
Context. Star and planet formation theories predict an evolution in the density, temperature, and velocity structure as the envelope collapses and forms an accretion disk. While continuum emission can trace the dust evolution, spectrally resolved molecular lines are needed to determine the physical structure and collapse dynamics. Aims. The aim of this work is to model the evolution of the molecular excitation, line profiles, and related observables during lowmass star formation. Specifically, the signatures of disks during the deeply embedded stage (Menv > M� ) are investigated. Methods. The semi-analytic 2D axisymmetric model of Visser and collaborators has been used to describe the evolution of the density, stellar mass, and luminosity from the pre-stellar to the T-Tauri phase. A full radiative transfer calculation is carried out to accurately determine the time-dependent dust temperatures. The time-dependent CO abundance is obtained from the adsorption and thermal desorption chemistry. Non-LTE near-IR (NIR), far-IR (FIR), and submm lines of CO have been simulated at a number of time steps. Results. In single dish (10−20 �� beams), the dynamics during the collapse are best probed through highly excited 13 CO and C 18 O lines, which are significantly broadened by the infall process. In contrast to the dust temperature, the CO excitation temperature derived from submm/FIR data does not vary during the protostellar evolution, consistent with C 18 O observations obtained with Herschel and from ground-based telescopes. The NIR spectra provide complementary information to the submm lines by probing not only the cold outer envelope but also the warm inner region. The NIR high-J (≥8) absorption lines are particularly sensitive to the physical structure of the inner few AU, which does show evolution. The models indicate that observations of 13 CO and C 18 Ol ow-J submm lines within a ≤1 �� (at 140 pc) beam are well suited to probe embedded disks in Stage I (Menv < M� ) sources, consistent with recent interferometric observations. High signal-to-noise ratio subarcsec resolution data with ALMA are needed to detect the presence of small rotationally supported disks during the Stage 0 phase and various diagnostics are discussed. The combination of spatially and spectrally resolved lines with ALMA and at NIR is a powerful method to probe the inner envelope and disk formation process during the embedded phase.