Feedback from OB stars on their parent cloud: gas exhaustion rather than gas ejection
Feedback from OB stars on their parent cloud: gas exhaustion rather than gas ejection
复制标题
DOI：
10.1051/0004-6361/201935277
复制
发表时间：
2019-06
影响因子：
6.5
通讯作者：
E. Watkins;N. Peretto;K. A. Marsh;G. Fuller
中科院分区：
文献类型：
--
作者：
E. Watkins;N. Peretto;K. A. Marsh;G. Fuller
上下文来自大质量恒星的反馈塑造了星际介质，从而影响了将形成未来恒星的气体。然而，由于我们无法跟踪单个分子云的时间演化，量化恒星反馈对其星星形成历史的确切作用是一项具有挑战性的观测任务。目标。在目前的研究中，我们利用G316.75-00.00恒星形成脊的独特性质，以确定来自O型恒星的恒星反馈如何影响大质量细丝的动力学稳定性。G316.75脊长13.6 pc，包含18900 M ²的H2气体，其中一半是红外暗的，一半是红外亮的。在过去的200万年里，红外亮部分已经形成了四颗O型星，而红外暗部分仍然处于静止状态。因此，通过假设红外暗部分的星星形成特性代表红外亮部分的早期演化阶段，我们可以通过对比两者来量化反馈如何影响这些特性。方法.我们使用公开可用的Herschel/HiGAL和分子线数据来测量整个海岭上每单位长度的动能与引力能之比αvirline。通过同时使用稠密的（如N2 H+和NH3）和更弥散的（如13 CO）气体示踪剂，我们能够计算出气体体积密度范围（~1 × 102-1 × 105 cm−3）的αvirline。结果这项研究表明，尽管存在四颗嵌入的O-星，但脊几乎在所有地方都保持引力束缚（即αvirline ≤ 2），除了高质量恒星附近的一些小气袋。事实上，αvirline在脊的两个部分几乎无法区分。这些结果与大多数流体动力学模拟不一致，在这些模拟中，O星形成云在几个云自由落体时间内被恒星反馈完全分散。然而，从简单的理论计算，我们表明，这种反馈效率低的情况下，预计高气体密度对流云。结论.我们的结论是，数值模拟和观测之间的差异，这里提出的起源于不同的云形态和平均密度的时候，第一个O型星的形式。在G316.75的情况下，我们推测脊可能是由云-云碰撞的后果产生的，并且这种附加的配置促进了恒星反馈的效率低下。这对已经存在的致密气体影响很小，但可能会阻止气体进一步积聚到山脊上。这些结果有重要的影响，例如，恒星反馈如何在宇宙学和星系尺度的模拟实施。
Context. Stellar feedback from high-mass stars shapes the interstellar medium, 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 stellar feedback on their star formation history is an observationally challenging task. Aims. In the present study, we take advantage of the unique properties of the G316.75-00.00 massive-star forming ridge to determine how stellar feedback from O-stars impacts the dynamical stability of massive filaments. The G316.75 ridge is 13.6 pc long and contains 18 900 M⊙ of H2 gas, half of which is infrared dark and half of which infrared bright. The infrared bright part has already formed four O-type stars over the past 2 Myr, while the infrared dark part is still quiescent. Therefore, by assuming the star forming properties of the infrared dark part represent the earlier evolutionary stage of the infrared bright part, we can quantify how feedback impacts these properties by contrasting the two. Methods. We used publicly available Herschel/HiGAL and molecular line data to measure the ratio of kinetic to gravitational energy per-unit-length, αvirline, across the entire ridge. By using both dense (i.e. N2H+ and NH3) and more diffuse (i.e. 13CO) gas tracers, we were able to compute αvirline for a range of gas volume densities (~1 × 102–1 × 105 cm−3). Results. This study shows that despite the presence of four embedded O-stars, the ridge remains gravitationally bound (i.e. αvirline ≤ 2) nearly everywhere, except for some small gas pockets near the high-mass stars. In fact, αvirline is almost indistinguishable for both parts of the ridge. These results are at odds with most hydrodynamical simulations in which O-star-forming clouds are completely dispersed by stellar feedback within a few cloud free-fall times. However, from simple theoretical calculations, we show that such feedback inefficiency is expected in the case of high-gas-density filamentary clouds. Conclusions. We conclude that the discrepancy between numerical simulations and the observations presented here originates from different cloud morphologies and average densities at the time when the first O-stars form. In the case of G316.75, we speculate that the ridge could arise from the aftermath of a cloud-cloud collision, and that such filamentary configuration promotes the inefficiency of stellar feedback. This does very little to the dense gas already present, but potentially prevents further gas accretion onto the ridge. These results have important implications regarding, for instance, how stellar feedback is implemented in cosmological and galaxy scale simulations.