AI 中文总结
研究亮边云SFO 25，利用JCMT-HARP观测其分子气体跃迁，结合盖亚视差确定位置。发现气体有头尾速度梯度，不符合RDI预期，头部、尾部和致密团块引力未束缚，恒星形成不限于头部，揭示其演化历史比经典模型更复杂。
AI 中文摘要
亮边云（BRCs）是研究大质量恒星的电离辐射如何重塑分子云并影响恒星形成的重要实验室。我们利用JCMT-HARP存档观测，对BRC SFO 25进行了运动学和动力学研究，观测了$^{12}$CO、$^{13}$CO和C$^{18}$O（$J = 3-2$）跃迁，角分辨率约为14-15弧秒（0.051-0.054 pc）。与云相关的年轻恒星天体的盖亚视差给出了修正距离，表明SFO 25位于电离O7V恒星HD 47839之后，意味着紫外线辐射可直接影响头部和尾部。分子气体呈现明显的头尾速度梯度，尾部相对于头部系统性红移，不符合经典辐射驱动内爆（RDI）预期，暗示处于由辐射扩散和光蒸发主导的演化阶段。头部比尾部密度稍大，与IRAS 06382+1017相关的致密C$^{18}$O团块密度达$10^4~\mathrm{cm}^{-3}$。维里和能量分析表明，头部、尾部和致密团块均为引力未束缚状态，动能超过引力束缚能和外部电离气体压力。在尾部识别出的II类年轻恒星天体候选者表明，恒星形成不限于致密头部。尽管RDI可能在头部触发了早期恒星形成，但无法轻易解释尾部观测到的活动，这表明其演化历史比经典RDI模型预测的更为复杂。
英文摘要
Bright-rimmed clouds (BRCs) are valuable laboratories for investigating how ionizing radiation from massive stars reshapes molecular clouds and influences star formation. We present a kinematic and dynamical study of the BRC SFO 25 using archival JCMT-HARP observations of the $^{12}$CO, $^{13}$CO, and C$^{18}$O ($J = 3-2$) transitions at an angular resolution of about 14-15 arcsec (0.051-0.054 pc). Gaia parallaxes of young stellar objects associated with the cloud yield a revised distance placing SFO 25 behind the ionizing O7V star HD 47839, implying that ultraviolet radiation can directly affect both the head and tail. The molecular gas exhibits a pronounced head-tail velocity gradient, with the tail systematically redshifted relative to the head, inconsistent with the expectations of classical radiation-driven implosion (RDI) and suggestive of an evolved phase dominated by radiative dispersal and photoevaporation. The head is moderately denser than the tail, while a compact C$^{18}$O clump associated with IRAS 06382+1017 reaches densities of $10^4~\mathrm{cm}^{-3}$. Virial and energy analyses indicate that the head, tail, and dense clump are gravitationally unbound, with kinetic energy exceeding both the gravitational binding energy and the external ionized gas pressure. Class II young stellar object candidates identified in the tail demonstrate that star formation is not confined to the dense head. Although RDI may have triggered earlier star formation in the head, it cannot readily explain the activity observed in the tail, pointing to a more complex evolutionary history than predicted by the classical RDI scenario.
Comments20 pages, 11 figures, Accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS)
