论文标题
速度梯度技术的协同作用和概率密度函数，以识别自我吸收介质中的重力崩溃
A Synergy of the Velocity Gradients Technique and the Probability Density Functions for Identifying Gravitational Collapse in Self-Absorbing Media
论文作者
论文摘要
质量密度的速度梯度技术（VGT）和概率密度函数（PDF）是研究分子云中湍流，磁场和自重的工具。但是，自我吸收可以显着使观察到的强度与柱密度结构不同。在这项工作中，我们研究了使用CO同位素的三个合成发射线$^{12} $ CO（1-0），$^{13} $ CO（1-0）和C $^{18} $ O（1-0）的自我吸收对VGT和强度PDF的影响。我们确认VGT的性能对辐射转移效应不敏感。我们从数值上显示了通过VGT构建3D磁场断层扫描的可能性。我们发现，强度PDFS从纯对数正常正常变为表现出幂律尾部的分布，具体取决于超音速湍流的光学深度。我们得出结论，CO同位素强度PDF的变化可以独立于自我重力，这使得强度PDF在识别引力崩溃区域中的可靠性降低。我们计算出星形成区域NGC 1333的强度PDF，并发现观察中强度PDF的变化与我们的数值结果一致。 VGT和柱密度PDF的协同作用证实，自我散热气体在NGC 1333中占据了很大的体积。
The Velocity Gradients Technique (VGT) and the Probability Density Functions (PDFs) of mass density are tools to study turbulence, magnetic fields, and self-gravity in molecular clouds. However, self-absorption can significantly make the observed intensity different from the column density structures. In this work, we study the effects of self-absorption on the VGT and the intensity PDFs utilizing three synthetic emission lines of CO isotopologs $^{12}$CO (1-0), $^{13}$CO (1-0), and C$^{18}$O (1-0). We confirm that the performance of VGT is insensitive to the radiative transfer effect. We numerically show the possibility of constructing 3D magnetic fields tomography through VGT. We find that the intensity PDFs change their shape from the pure log-normal to a distribution that exhibits a power-law tail depending on the optical depth for supersonic turbulence. We conclude the change of CO isotopologs' intensity PDFs can be independent of self-gravity, which makes the intensity PDFs less reliable in identifying gravitational collapsing regions. We compute the intensity PDFs for a star-forming region NGC 1333 and find the change of intensity PDFs in observation agrees with our numerical results. The synergy of VGT and the column density PDFs confirms that the self-gravitating gas occupies a large volume in NGC 1333.
