论文标题
hcn $ j $ = 4-3，hnc $ j $ = 1-0，$ \ mathrm {h^{13} cn} $ $ $ j $ = 1-0，以及$ \ mathrm {hc_3n} $ $ $ j $ = 10-9个银河系中心的地图II。ii。：：
HCN $J$=4-3, HNC $J$=1-0, $\mathrm{H^{13}CN}$ $J$=1-0, and $\mathrm{HC_3N}$ $J$=10-9 Maps of Galactic Center Region II.: Physical Properties of Dense Gas Clumps and Probability of Star Formation
论文作者
论文摘要
We report a statistical analysis exploring the origin of the overall low star formation efficiency (SFE) of the Galactic central molecular zone (CMZ) and the SFE diversity among the CMZ clouds using a wide-field HCN $J$=4-3 map, whose optically thin critical density ($\sim10^7\,\mathrm{cm}^{-3}$) is the highest among the tracers ever used in CMZ调查。进行逻辑回归以经验表达195 HCN团块的恒星形成概率，其中13个包含恒星形成特征。最佳拟合模型中的解释性参数被简化为病毒参数$α_ {\ mathrm {vir}} $，而没有其他参数的重大贡献，而没有$α_{\ mathrm {vir}} $的模型的性能比使用随机生成的数据更好。阈值$α_ {\ mathrm {vir}} $是6，它转化为$ 10^{4.6} \，\ Mathrm {cmmathrm {cm}^{cm}^{ - 3} $的体积密度（$ n _ {\ Mathrm {\ Mathrm {h_2}} $） $ n _ {\ mathrm {h_2}} $ - $α_ {\ mathrm {vir}} $相关。低 - $α_ {\ mathrm {vir}} $团块的稀缺性，其对所有HCN团的分数均为0.1，被视为被抑制SFE的直接原因之一。没有发现团块大小或质量和恒星形成概率之间的相关性，这意味着HCN $ j $ = 4-3不会立即跟踪阈值高于阈值的恒星形成气体的质量。同时，在CS $ \ Mathit {J} $ = 1-0云的物理参数中，恒星形成和非星形形成云是退化的，突出了HCN $ \ Mathit {J J} $ = 4-3线以探测CMZ中的星形星形区域的功效。 The time scale of the high-$α_{\mathrm{vir}}$ to low-$α_{\mathrm{vir}}$ transition is $\lesssim2$ Myr, which is consistent with the tidal compression and X1/X2 orbit transition models but possibly does not fit the cloud-cloud collision picture.
We report a statistical analysis exploring the origin of the overall low star formation efficiency (SFE) of the Galactic central molecular zone (CMZ) and the SFE diversity among the CMZ clouds using a wide-field HCN $J$=4-3 map, whose optically thin critical density ($\sim10^7\,\mathrm{cm}^{-3}$) is the highest among the tracers ever used in CMZ surveys. Logistic regression is performed to empirically formulate star formation probability of 195 HCN clumps, 13 of which contain star formation signatures. The explanatory parameters in the best-fit model are reduced into the virial parameter $α_{\mathrm{vir}}$ without significant contribution from other parameters, whereas the performance of the model without $α_{\mathrm{vir}}$ is no better than that using randomly generated data. The threshold $α_{\mathrm{vir}}$ is 6, which translates into a volume density ($n_{\mathrm{H_2}}$) of $10^{4.6}\,\mathrm{cm}^{-3}$ with the $n_{\mathrm{H_2}}$-$α_{\mathrm{vir}}$ correlation. The scarcity of the low-$α_{\mathrm{vir}}$ clumps, whose fraction to all HCN clumps is 0.1, can be considered as one of the immediate causes of the suppressed SFE. No correlation between the clump size or mass and star formation probability is found, implying that HCN $J$=4-3 does not immediately trace the mass of star-forming gas above a threshold density. Meanwhile, star-forming and non-star-forming clouds are degenerate in the physical parameters of the CS $\mathit{J}$=1-0 clouds, highlighting the efficacy of the HCN $\mathit{J}$=4-3 line to probe star-forming regions in the CMZ. The time scale of the high-$α_{\mathrm{vir}}$ to low-$α_{\mathrm{vir}}$ transition is $\lesssim2$ Myr, which is consistent with the tidal compression and X1/X2 orbit transition models but possibly does not fit the cloud-cloud collision picture.
