论文标题
巨型分子丝中的致密气
Dense Gas in a Giant Molecular Filament
论文作者
论文摘要
最近对粉尘连续和共同排放线的银河飞机进行的调查表明，大型（$ \ gtrsim 50 $ 〜p PC）和巨大（$ \ gtrsim 10^5 $〜$〜$〜$〜$〜$ m_ \ odot $）细丝，被称为巨型分子细丝（GMF），可能会与循环的元素和循环范围内的元素相关。我们已经成像了一个整个GMF，位于$ l \ sim $ 52--54 $^\ Circ $经度，GMF54（$ \ sim $ 68〜PC长），在经验性的密集加油示踪剂中，使用HCN（1---0），HNC（1--0），HNC（1--0），HCO $ $^+$^+$^+$^+$^+$^+$（1---0）和$^is $^istrient and $^; n $ _2 $ h $^+$（1--0）行。我们研究了密度的气体分布，柱密度概率密度函数（N-PDF）和GMF内的线比。相对于$^{13} $ CO（1--0），密集的气体分子过渡遵循细丝的扩展结构，面积填充因子在0.06至0.28之间。我们根据其圆柱密度并假定均匀的丰度为每个密集的气体示踪剂构建了H $ _2 $的N-PDF。密集的气体示踪剂的N-PDF在日志表现中弯曲，而HCO $^+$ n-PDF具有最大的对数正态宽度和最平坦的幂律坡度索引。在研究GMF54子区域的N-PDF时，我们发现N-PDF的进化趋势是，高质量恒星形成和光子含量区域（PDR）具有平坦的幂律指数。 GMF54中分子线的集成强度比与附近星系中的综合强度比相当。特别是，追踪密度的气体分数的n $ _2 $ h $^+$/$^{13} $ co比率在GMF54中具有相似的值，除了Ulirgs以外的所有附近星系。
Recent surveys of the Galactic plane in the dust continuum and CO emission lines reveal that large ($\gtrsim 50$~pc) and massive ($\gtrsim 10^5$~$M_\odot$) filaments, know as giant molecular filaments (GMFs), may be linked to galactic dynamics and trace the mid-plane of the gravitational potential in the Milky Way. We have imaged one entire GMF located at $l\sim$52--54$^\circ$ longitude, GMF54 ($\sim$68~pc long), in the empirical dense gas tracers using the HCN(1--0), HNC(1--0), HCO$^+$(1--0) lines, and their $^{13}$C isotopologue transitions, as well as the N$_2$H$^+$(1--0) line. We study the dense gas distribution, the column density probability density functions (N-PDFs) and the line ratios within the GMF. The dense gas molecular transitions follow the extended structure of the filament with area filling factors between 0.06 and 0.28 with respect to $^{13}$CO(1--0). We constructed the N-PDFs of H$_2$ for each of the dense gas tracers based on their column densities and assumed uniform abundance. The N-PDFs of the dense gas tracers appear curved in log-log representation, and the HCO$^+$ N-PDF has the largest log-normal width and flattest power-law slope index. Studying the N-PDFs for sub-regions of GMF54, we found an evolutionary trend in the N-PDFs that high-mass star forming and Photon-Dominate Regions (PDRs) have flatter power-law indices. The integrated intensity ratios of the molecular lines in GMF54 are comparable to those in nearby galaxies. In particular, the N$_2$H$^+$/$^{13}$CO ratio, which traces the dense gas fraction, has similar values in GMF54 and all nearby galaxies except ULIRGs.
