Feedback from high-mass stars shapes the ISM of galaxies and thereby impacts gas that will form future generations of stars. However, due to our inability to track the time evolution of individual molecular clouds, quantifying the exact role of feedback on their star formation history is an observationally challenging task. In the present study, we take advantage of the unique properties of the G316.75-00.00 high-mass star-forming ridge to determine how feedback from O-stars impacts the dynamical stability of filaments. G316.75 is a 13.6pc long ridge containing 18,900Msun of H2 gas which is half IR dark, half IR bright. The IR bright half has already formed 4 O-type stars over the past 2Myr, while the IR dark half is still quiescent. Therefore, by assuming the gas properties of the dark part represents an earlier evolutionary stage of the bright part, we can quantify how feedback impacts these properties by contrasting them. We use archive Herschel and molecular line data, tracing both dense (NH3 and N2H+) and more diffuse (13CO) gas, to measure the ratio of kinetic to gravitational energy per-unit-length, virial-ratio-per-line, across the ridge for a range of gas volume densities. We show that despite the presence of 4 embedded O-stars, feedback cannot unbind the ridge's mass except for some small gas pockets near the O-stars. In fact, the virial-ratio-per-line is almost indistinguishable for both parts of the ridge. These results are at odds with most simulations where O-star-forming clouds are dispersed by feedback within a few cloud free-fall time. We conclude that the discrepancy between such simulations and our observations originates from different cloud morphologies and average densities when the first O-star forms. These results have important implications regarding, for instance, how feedback is implemented within cosmological and galactic-scale simulations.
Runaway OB Stars in the Small Magellanic Cloud: Dynamical Versus Supernova Ejections
逃逸的OB星通过两种机制从它们的母星团中弹射出来，这两种机制都涉及多颗恒星：动力学弹射情景（DES）和双星超新星情景（BSS）。我们约束的相对贡献，这两个弹射机制在小麦哲伦云（SMC）使用的数据为304场OB星的空间完整，失控和孤立的O型星光谱调查的SMC（RIOTS 4）。我们获得恒星质量和投影旋转速度$v_r\sin i $的样品使用RIOTS 4光谱，并使用横向速度$v_{\rm loc}$从$\it{Gaia}$ DR 2自行。运动学分析的群众，$v_r\sin i $，非紧凑型双星，高质量的X射线双星，和Oe/Be星在很大程度上支持DES和BSS人口的统计特性的预测。我们发现，动力学喷射占主导地位的超新星喷射的一个因素的$\sim 2-3$在SMC，我们的研究结果表明，DES逃逸和二进制喷射的频率很高。被视为BSS失控的对象还包括由SN踢重新加速的二进制文件的两步喷射。我们发现，两步离家出走可能占主导地位的BSS失控人口。我们的研究结果进一步表明，任何贡献，从$\it{in-situ}$领域OB星的形成是小的。最后，我们的数据强烈支持后质量转移模型的起源经典的Oe/Be星，提供了一个简单的解释双峰的$v_r\sin i $分布和高，近临界，Oe/Be旋转速度。Oe/Be星与BSS预测的密切对应意味着发射线盘是长寿命的。
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（同济大学李政道研究所，上海交通大学）；Center for Astrophysics and Planetary Science, Department of Astronomy, Cornell University（康奈尔大学天文学系天体物理学与行星科学中心）
