PRODIGE——利用NOEMA观测从包层到盘体III. SVS13A中复杂有机分子发射的起源
PRODIGE -- Envelope to Disk with NOEMA III. The origin of complex organic molecule emission in SVS13A
AI总结：
本研究利用PRODIGE项目的NOEMA观测分析SVS13A的6种含氧复杂有机分子，通过多速度分量LTE拟合发现中心区域结构非均匀，大尺度下落流引发的吸积激波可能是COM发射复杂的原因。
摘要：
复杂有机分子（COMs）已在低质量原恒星周围被发现，但COM发射的起源仍不明确。它可能与热星核、外流、吸积激波/盘大气等相关。我们利用来自“原恒星与盘：全球演化（PRODIGE）”项目的NOEMA观测数据，对SVS13A开展了研究。我们此前的\ue010DCN观测揭示了一条可能的下落流，它可能通过引发吸积爆发和/或受激气体影响中心原双星的化学组成。在此，我们进一步分析了6种含氧COM：CH3OH、aGg'-(CH2OH)2、C2H5OH、CH2(OH)CHO、CH3CHO和CH3OCHO。尽管COM发射未被空间分辨，但我们通过紫外域高斯拟合将源尺寸限制在≲0.3-0.4角秒（90-120天文单位）。有趣的是，高光谱分辨率数据揭示了具有多峰的复杂谱线轮廓，这6种含氧COM之间存在差异。局域热动平衡（LTE）拟合揭示了这些COM的激发温度和发射区域存在差异。我们进一步开展了多速度分量LTE拟合，将谱线发射分解为不同的运动学分量。LTE建模最多发现了6个速度分量，得到了每种COM对应这些分量的温度、柱密度和源尺寸。我们发现，来自不同COM的这些运动学分量的激发温度（100-500 K）和源尺寸（直径D~10-70天文单位）存在多样性。每种COM的发射都可以示踪多个分量，且不同的COM极有可能示踪不同的区域。鉴于这种复杂结构，我们认为中心区域是非均匀的，不太可能仅由原恒星辐射加热。我们得出结论：由大尺度下落流引发的吸积激波很可能存在，并促成了COM发射的复杂性。
英文摘要：
Complex Organic Molecules (COMs) have been found toward low-mass protostars but the origins of the COM emission are still unclear. It can be associated with, for example, hot corinos, outflows, and/or accretion shock/disk atmosphere. We have conducted NOEMA observations toward SVS13A from the PROtostars & DIsks: Global Evolution (PRODIGE) program. Our previous \ce{DCN} observations reveal a possible infalling streamer, which may affect the chemistry of the central protobinary by inducing accretion outbursts and/or shocked gas. Here, we further analyze six O-bearing COMs: CH3OH, aGg'-(CH2OH)2, C2H5OH, CH2(OH)CHO, CH3CHO, and CH3OCHO. Although the COM emission is not spatially resolved, we constrain the source sizes to $\lesssim0.3-0.4$ arcsec (90$-$120 au) by conducting uv-domain Gaussian fitting. Interestingly, the high-spectral resolution data reveal complex line profiles with multiple peaks showing differences between these six O-bearing COMs. The LTE fitting unveils differences in excitation temperatures and emitting areas among these COMs. We further conduct multiple-velocity-component LTE fitting to decompose the line emission into different kinematic components. Up to 6 velocity components are found from the LTE modeling. The temperature, column density, and source size of these components from each COM are obtained. We find a variety in excitation temperatures ($100-500$ K) and source sizes (D$\sim10-70$ au) from these kinematic components from different COMs. The emission of each COM can trace several components and different COMs most likely trace different regions. Given this complex structure, we suggest that the central region is inhomogeneous and unlikely to be heated by only protostellar radiation. We conclude that accretion shocks induced by the large-scale infalling streamer likely exist and contribute to the complexity of the COM emission.
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