ALMA EGO-10 大质量原星团巡天：1.3毫米连续谱源成团性与演化状态的关联
The ALMA EGO-10 Survey of Massive Protoclusters: Correlation of 1.3 mm Continuum Source Clustering with Evolutionary State
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中文总结 AI 辅助
该研究通过ALMA EGO-10巡天观测10个EGO原星团，构建新演化指标L_cm/M_AGAL，发现其与Q参数正相关，揭示原星团从亚成团到中心致密的演化规律，支持层级式团块吸积模型。
中文摘要 AI 辅助
大质量恒星通常形成于成团环境中，因此表征年轻大质量“原星团”对于限制大质量恒星形成机制以及恒星团的形成过程至关重要。我们公布了ALMA EGO-10成像巡天的1.3毫米连续谱结果，该巡天的目标是10个斯皮策GLIMPSE扩展绿天体（EGOs）——即拥有由延展4.5微米发射所示踪的活跃外流的大质量原恒星。我们的高灵敏度1'.6×1'.6拼接图像显示所有目标都关联着丰富的原星团。在平均空间分辨率为2200×1600天文单位的条件下，我们识别出570个核，每个天区的核数量在13到135个之间。我们用Q参数量化原星团结构，发现结构存在多样性，Q值范围为0.5≲Q≲0.9。该样本的显著特点是拥有丰富的互补高分辨率多波段数据。将我们识别的核与这些观测结果关联后发现，仅有2%、5%和4%的核分别拥有6.7 GHz CH₃OH脉泽、22 GHz H₂O脉泽和厘米波段连续谱源。由6.7 GHz脉泽示踪的大质量原恒星通常位于原星团中心附近（中位偏移量为0.045秒差距），且所有距离小于3千秒差距的此类原恒星都处于成团环境中，在10000天文单位范围内有超过10个核。利用VLA厘米波段连续谱观测，我们构建了一个新的演化指标：原星团厘米波段连续谱光度与关联的ATLASGAL团块质量的比值（L_cm/M_AGAL）。该比值与Q参数呈正相关，这一相关性主要由大质量年轻恒星（MYSOs）的厘米波段连续谱发射驱动。这表明原星团结构是动态的，会从亚成团结构演变为中心致密结构，与大质量恒星形成的层级式团块吸积模型中的全局坍缩一致。
英文摘要
Massive stars characteristically form in clustered environments. Characterising young massive 'protoclusters' is therefore crucial to constraining the mechanism(s) of massive star formation, and of the assembly of stellar clusters. We present 1.3 mm continuum results from the ALMA EGO-10 imaging survey, targeting ten Spitzer GLIMPSE Extended Green Objects (EGOs) - massive protostars with active outflows traced by extended 4.5 $μ$m emission. Our sensitive 1'.6$\times$1'.6 mosaics reveal rich protoclusters associated with all targets. With a mean spatial resolution 2200$\times$1600 AU, we identify 570 cores - between 13 and 135 per field. We quantify protocluster structure with the $Q$-parameter, finding structural diversity with 0.5 $\lesssim Q \lesssim$ 0.9. The sample is notable for the wealth of complementary high-resolution multiwavelength data available. Correlating our cores with these observations, we find only 2%, 5% and 4% of cores host 6.7 GHz CH$_3$OH masers, 22 GHz H$_2$O masers and cm-$λ$ continuum sources, respectively. The massive protostars traced by 6.7 GHz masers typically reside near protocluster centres (median offset 0.045 pc), and all at $d<$ 3 kpc are found in clustered locales, with $>$10 cores within 10,000 AU. Using VLA cm-$λ$ continuum observations, we construct a new evolutionary indicator: the ratio of protocluster cm-$λ$ continuum luminosity to the mass of the associated ATLASGAL clump ($L_\text{cm}/M_\text{AGAL}$). This ratio correlates positively with $Q$, with the correlation driven primarily by the cm-$λ$ continuum emission from MYSOs. This suggests dynamic protocluster structure, evolving from subclustered to centrally condensed, consistent with the global collapse in hierarchical, clump-fed models of massive star formation.
