W49A分子云复合体中的热分子核
Hot molecular cores in the W49A molecular cloud complex
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中文总结 AI 辅助
该研究基于ALMA观测构建W49A分子云HMCs综合数据集，明确其5个结构区域，得出CH₃CN丰度与温度的经验关系，发现无H/UCHII区的HMCs寿命更长，为相关吸积模型提供参考。
中文摘要 AI 辅助
我们基于高分辨率ALMA观测，发布了W49A分子云复合体中热分子核（HMCs）的综合数据集，包括1.3毫米连续谱、12条分子线和H30α复合线。在CH₃CN（J_K=12₃-11₃）图中总共识别出18个HMCs，同时在1.3毫米图中识别出20个连续谱源。10个HMCs的峰值与1.3毫米连续谱峰值在0.1角秒内重合，表明这些源的1.3毫米辐射以热尘埃辐射为主。线光度的相关分析表明HMCs存在共同的结构图像，其中共存着5个具有不同物理和化学性质的不同区域：热密气体（CH₃CN、HC₃N、HNCO、OCS、H₂CO）、外流气体（SiO、SO）、包层气体（SO₂、CH₃OH）、延展气体（¹³CS、DCN、C¹⁸O）和电离气体（H30α）。我们发现CH₃CN的分丰度与转动温度之间存在经验关系X(CH₃CN)=2.5×10⁻⁷exp[-490/T_rot]，表明要达到~10⁻⁷的高分丰度需要T≳200-300开尔文。我们还发现，没有嵌入H/UCHII区的HMCs数量多于或至少与带有此类区的HMCs相当，这表明前者的寿命（~10⁵年）可能比后者（~10⁴年）更长。我们讨论了这些结果对核吸积和竞争吸积模型的意义。
英文摘要
We present a comprehensive dataset of hot molecular cores (HMCs) in the W49A molecular cloud complex based on high-resolution ALMA observations, including the 1.3~mm continuum, 12 molecular lines, and the H30alpha recombination line. In total, 18 HMCs are identified in the CH$_{3}$CN ($J_K=12_3-11_3$) map, together with 20 continuum sources in the 1.3~mm map. Ten HMCs have peaks coincident within 0\farcs1 of the 1.3~mm continuum peaks, indicating that thermal dust emission dominates the 1.3~mm emission for these sources. Correlation analyses of the line luminosities suggest a common structural picture for HMCs, in which five distinct regions with different physical and chemical properties coexist: hot and dense gas (CH$_3$CN, HC$_3$N, HNCO, OCS, H$_2$CO), outflow gas (SiO, SO), envelope gas (SO$_2$, CH$_3$OH), extended gas ($^{13}$CS, DCN, C$^{18}$O), and ionized gas (H30alpha). We find an empirical relation $X(\mathrm{CH_3CN})=2.5\times10^{-7}\exp[-490/T_\mathrm{rot}]$ between the fractional abundance and rotation temperature of CH$_{3}$CN, suggesting that $T\gtrsim200$--300~K is required to achieve high abundances of $\sim10^{-7}$. We find that HMCs without embedded H/UCHII regions are more numerous than, or at least comparable in number to, HMCs with such regions, suggesting that the former may have longer lifetimes ($\sim$10$^{5}$~yr) than the latter ($\sim$10$^{4}$~yr). We discuss the implications of these results for the core accretion and competitive accretion models.
