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DIPSY：一种新的盘不稳定性人口合成，II. 通过盘不稳定性形成伴星的人口

DIPSY: A new Disc Instability Population SYnthesis, II. The Populations of Companions Formed Through Disc Instability

University of Bern（伯尔尼大学）；Universität Zürich（苏黎世大学）

O. Schib, C. Mordasini, A. Emsenhuber, R. Helled

备注：
Accepted for publication in A&A
发表信息：
A&A 704, A28 (2025)
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AI总结：

DIPSY研究通过盘不稳定性形成伴星的人口，发现远距离伴星主要由盘不稳定性形成，但近距离行星质量伴星稀少，需进一步研究气体吸积和团块碰撞等关键过程。

摘要：

我们应用了本系列论文I中描述的全局端到端模型，对通过盘不稳定性（DI）形成伴星的人口进行了合成。通过使用与观测和流体动力学模拟相容的初始条件，并研究了广泛的主要质量范围（0.05-5 M_sol），我们可以提供DI结果的定量预测。在基线人口中，我们发现约10%的盘会发生碎片化，其中大约一半的碎片在1亿年（Myr）后仍保留有伴星。75%的伴星处于褐矮星范围，15%是低质量恒星，10%是行星。在距离大于约100天文单位（AU）处，DI会产生行星质量的伴星，但比例较低。然而，在100 AU以内，行星质量的伴星非常稀少（每千分之一级别）。平均伴星质量约为30 M_j，与恒星质量呈弱相关。大多数初始碎片在Myr时间尺度上无法存活；它们要么与其他碎片碰撞，要么被弹射，导致自由漂浮物体的人口（大约每颗恒星1-2个）。我们还量化了若干变种人口，以批判性地评估我们在基线人口中使用的某些假设。DI似乎在形成质量从低质量恒星到行星范围的远距离伴星中起关键作用，但对100 AU以内行星质量的物体贡献有限。我们的结果对多种物理过程敏感，其中一些尚未完全理解。其中两个，气体吸积和团块-团块碰撞，特别重要，需要进一步研究。磁力场和重元素吸积在我们的研究中未被考虑，尽管它们也预计会影响推断的人口。我们建议承认重力湍流阶段的重要性，这是大多数原行星盘经历的阶段。

英文摘要：

We applied the global end-to-end model described in Paper~I of this series to perform a population synthesis of companions formed via disc instability (DI). By using initial conditions compatible with both observations and hydrodynamical simulations, and by studying a large range of primary masses (0.05-5 Msol), we can provide quantitative predictions of the outcome of DI. In the baseline population, we find that ~10 % of the discs fragment, and about half of these end up with a surviving companion after 100 Myr. 75\% of the companions are in the brown dwarf regime, 15 % are low-mass stars, and 10 % planets. At distances larger than ~100 au, DI produces planetary-mass companions on a low percent level. Inside of 100 AU, however, planetary-mass companions are very rare (low per mill level). The average companion mass is ~30 Mj scaling weakly with stellar mass. Most of the initial fragments do not survive on a Myr timescale; they either collide with other fragments or are ejected, resulting in a population of free-floating objects (about 1-2 per star). We also quantify several variant populations to critically assess some of our assumptions used in the baseline population. DI appears to be a key mechanism in the formation of distant companions with masses ranging from low-mass stars down to the planetary regime, contributing, however, only marginally to planetary mass objects inside of 100 AU. Our results are sensitive to a number of physical processes, which are not completely understood. Two of them, gas accretion and clump-clump collisions, are particularly important and need to be investigated further. Magnetic fields and heavy-element accretion have not been considered in our study, although they are also expected to affect the inferred population. We suggest acknowledging the importance of the gravito-turbulent phase, which most protoplanetary discs experience.

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