论文标题
低金属气体云中原恒星系统的光盘破碎和寡头生长
Disc fragmentation and oligarchic growth of protostellar systems in low-metallicity gas clouds
论文作者
论文摘要
我们研究了低分辨率的恒星形成，并使用一组高分辨率的流体动力学模拟，用于各种气体金属，范围内$ 0 $ - $ 10^{ - 3} \ {\ rm z} _ {\ bigodot} $。我们的模拟通过采用逼真的元素丰度和灰尘尺寸分布，遵循非平衡化学和辐射冷却。我们研究了塌陷云（云破碎； CF）和增生盘（盘片段化； DF）的碎片条件。我们发现，即使有有效的金属粉尘冷却$ \ gtrsim 10^{ - 5} \ {\ rm z} _ {\ bigodot} $，CF也会抑制CF，即使具有有效的金属粉尘冷却$ \ gtrsim 10^{ - 5} \ {\ bigodot} $，也会受到分子氢的形成。取而代之的是，无论金属性如何，DF几乎在所有运行中都会发生。我们还发现，在积聚盘中，原始系统的生长总体上是寡头的。主要的原始质体通过气体积聚生长，次级原恒星通过螺旋臂的相互作用或快速旋转的原恒星的分裂形成。尽管有剧烈的破碎，但大量的次级原恒星通过合并或潮汐破坏事件破坏。在第一个绝热核心形成后的几百年里，只有几个原始的原始恒星在光盘中生存，而原恒星的总质量为$ 0.52 $ - $ 3.8 \ {\ rm m} _ {\ bigodot} $。
We study low-metallicity star formation with a set of high-resolution hydrodynamics simulations for various gas metallicities over a wide range $0$--$10^{-3} \ {\rm Z}_{\bigodot}$. Our simulations follow non-equilibrium chemistry and radiative cooling by adopting realistic elemental abundance and dust size distribution. We examine the condition for the fragmentation of collapsing clouds (cloud fragmentation; CF) and of accretion discs (disc fragmentation; DF). We find that CF is suppressed due to rapid gas heating accompanied with molecular hydrogen formation even with efficient dust cooling for metallicities $\gtrsim 10^{-5} \ {\rm Z}_{\bigodot}$. Instead, DF occurs in almost all runs regardless of metallicity. We also find that, in the accretion discs, the growth of the protostellar systems is overall oligarchic. The primary protostar grows through the accretion of gas, and secondary protostars form through the interaction of spiral arms or the break-up of a rapidly rotating protostar. Despite vigorous fragmentation, a large fraction of secondary protostars are destroyed through mergers or tidal disruption events. For a few hundred years after the first adiabatic core formation, only several protostars survive in the disc, and the total mass of protostars is $0.52$--$3.8 \ {\rm M}_{\bigodot}$.
