大质量恒星形成始于亚维里致密团块，除非受到强磁场的阻碍
Massive Star Formation Starts in Sub-virial Dense Clumps Unless Resisted by Strong Magnetic Fields
AI总结：
本研究利用RAMPS巡天的氨分子谱线数据，统计发现大质量无恒星团块多处于亚维里引力束缚态，挑战了维里平衡理论，表明大质量恒星形成始于亚维里致密团块，或需强磁场支撑抵抗坍缩。
摘要：
初始条件对于理解大质量恒星形成至关重要，但尚未得到充分观测。基于我们此前对银河系范围内463个大质量无恒星团块候选体（HMSCs）样本的表征研究，本文利用来自射电氨分子中平面巡天（RAMPS）试点数据发布的GBT NH₃（1,1）和（2,2）数据，研究了44个具有代表性的HMSCs子样本（半径0.13-1.12 pc）的动力学状态。通过同时拟合两条NH₃谱线，我们获得了速度弥散、气体动力学温度、NH₃柱密度与丰度、马赫数以及维里参数。热力学分析显示，大多数HMSCs的马赫数<5，这与理论模型中的普遍假设不一致。除一个样本外（43/44），所有HMSCs均为引力束缚态，维里参数αᵥᵢᵣ < 2。这意味着要么这些大质量团块正处于坍缩过程中，要么需要0.10-2.65 mG（平均0.51 mG）的磁场强度来支撑它们抵抗坍缩。估算得到的磁场强度与密度紧密相关，满足关系式Bₑₛₜ/mG=0.269(n_H₂/10⁴ cm⁻³)^0.61，其幂律指数与观测结果相近，但强度高出4.6倍。本研究首次从统计上将大质量恒星形成区的初始动力学状态约束为亚维里态，这与维里平衡的理论模型相矛盾，却与未观测到大质量无恒星星核的现象相符。这些发现推动未来的观测需量化大质量团块在预恒星阶段的磁场支撑作用——该领域目前鲜有探索——以全面理解触发大质量恒星形成的物理条件。
英文摘要：
The initial conditions are critical for understanding high-mass star formation, but are not well observed. Built on our previous characterization of a Galaxy-wide sample of 463 candidate high-mass starless clumps (HMSCs), here we investigate the dynamical state of a representative subsample of 44 HMSCs (radii 0.13-1.12 pc) using GBT NH3 (1,1) and (2,2) data from the Radio Ammonia Mid-Plane Survey (RAMPS) pilot data release. By fitting the two NH3 lines simultaneously, we obtain velocity dispersion, gas kinetic temperature, NH3 column density and abundance, Mach number, and virial parameter. Thermodynamic analysis reveals that most HMSCs have Mach number $<$5, inconsistent to what have been considered in theoretical models. All but one (43/44) of the HMSCs are gravitationally bound with virial parameter $α_{\mathrm{vir}} < 2$. Either these massive clumps are in collapsing or magnetic field strengths of 0.10-2.65 mG (average 0.51 mG) would be needed to support them against collapsing. The estimated B-field strength correlates tightly with density, $B_{\rm est}/{\rm mG}=0.269\,(n_{\rm H_2}/10^4\,{\rm cm^{-3}})^{0.61}$, with a similar power-law index as found in observations, but a factor of 4.6 higher in strength. For the first time, the initial dynamical state of high-mass formation regions has been statistically constrained to be sub-virial, in contradictory to theoretical models in virial equilibrium, and in agreement with the lack of observed massive starless cores. The findings urge future observations to quantify the magnetic field support in the prestellar stage of massive clumps, which are rarely explored so far, towards a full understanding of the physical conditions that initiate massive star formation.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
