AI 中文总结
本研究利用GASKAP-HI巡天数据，分析大麦哲伦云的冷原子气体性质，明确其与分子气体、恒星形成的关联，揭示冷原子气体的运动学特征及相关物理机制。
AI 中文摘要
我们利用 GASKAP-HI 巡天的氢原子（HI）吸收探测结果，研究大麦哲伦云（LMC）内冷原子气体的性质。采用辐射传输方法，我们将155条视线分解为330个冷中性介质（CNM）、2个热不稳定中性介质（UNM）和310个暖中性介质（WNM）成分。研究发现，与银河系相比，LMC中的CNM表现出更高的光学深度（中位数0.46）、更低的自旋温度（中位数~37 K）、更宽的线宽（中位数~4.9 km s⁻¹），以及略低的CNM占比（中位数~23%）。我们考察了CNM、分子气体与恒星形成之间的关联，发现CNM与分子气体的相关性比WNM更紧密，而分子气体与恒星形成的关系则更为密切。分子氢（H₂）在N_{HI,CNM}~10²⁰ cm⁻²附近开始形成，几乎所有N_{HI,CNM}>10²¹ cm⁻²的视线都包含分子气体。CNM占比随消光量（A_V）增加而上升，且在显著更低的A_V下，LMC的CNM占比与银河系相当，这可能源于更高的局部密度和更长的视线深度。膨胀壳附近的视线往往呈现更高的CNM占比，尽管部分由更高的总HI柱密度驱动。最后，CNM的运动学通常遵循HI盘旋转，约7%的成分表现出大于25 km s⁻¹的速度偏移，可能示踪由恒星反馈或麦哲伦系统内大尺度相互作用引发的流入或流出。
英文摘要
We use atomic hydrogen (HI) absorption detections from the GASKAP-HI survey to investigate the properties of cold atomic gas in the Large Magellanic Cloud (LMC). Using the radiative transfer method, we decompose 155 sightlines into 330 cold neutral medium (CNM), 2 thermally unstable neutral medium (UNM), and 310 warm neutral medium (WNM) components. We find that the CNM in the LMC exhibits higher optical depths (median 0.46), lower spin temperatures (median $\sim$37 K), broader linewidths (median $\sim$4.9 km s$^{-1}$), and slightly lower CNM fractions (median $\sim$23%) than in the Milky Way. We examine the connection between the CNM, molecular gas, and star formation, finding that CNM correlates more closely with molecular gas than WNM, while molecular gas shows a tighter relation with star formation. Molecular hydrogen (H$_2$) formation begins near $N{_\mathrm{HI,CNM}}\sim10^{20}~\mathrm{cm^{-2}}$, and nearly all sightlines with $N_{\mathrm{HI,CNM}}>10^{21}~\mathrm{cm^{-2}}$ contain molecular gas. The CNM fraction increases with visual extinction ($A_V$), and the LMC maintains CNM fractions comparable to those in the Milky Way at substantially lower $A_V$, likely due to higher local densities and a longer line-of-sight depth. Sightlines near expanding shells tend to show higher CNM fractions, although this is partly driven by higher total HI column densities. Finally, the CNM kinematics generally follow the HI disk rotation, with about 7% of components showing velocity offsets greater than $25~\mathrm{km~s^{-1}}$, likely tracing inflows or outflows driven by stellar feedback or large-scale interactions within the Magellanic System.
Comments36 pages, 20 figures, 3 tables. Accepted for publication in ApJ
