Pebble accretion in Class 0/I YSOs as a possible pathway for early planet formation
Pebble accretion in Class 0/I YSOs as a possible pathway for early planet formation
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DOI：
10.1093/mnras/stz069
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发表时间：
2019-01
影响因子：
4.8
通讯作者：
Yuki A. Tanaka;Y. Tsukamoto
中科院分区：
文献类型：
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作者：
Yuki A. Tanaka;Y. Tsukamoto
最近的理论工作表明，鹅卵石吸积过程对原行星盘中行星的形成很重要，因为它加速了行星核心的生长。而几次观测显示，在非常年轻的圆盘上存在轴对称的尖锐缝隙，这可能表明行星的存在。我们研究了在更早的阶段通过卵石吸积形成行星的可能性，这是0/I类年轻恒星物体的引力不稳定盘。我们发现，在0/I类盘的条件下，由于气体和尘埃的吸积速率较大，鹅卵石的吸积时间尺度可以比典型的原行星盘短，但也发现吸积时间尺度并不总是气体吸积速率的递减函数。通过使用估计的吸积时间尺度，我们在几个参数下给出了在0/I类阶段生命周期内形成气体巨星核心所需的初始质量，例如与主恒星的径向距离，气体吸积速率和尘埃与气体的质量比。在最乐观的情况下，例如尘埃与气体的质量比为$f=3f_{\rm solar}$，在0/I类阶段（0.5 Myr）的典型寿命期间，10 au处的$\sim10^{-4}M_{\oplus}$物体可以增长到$10M_{\oplus}$核。
Recent theoretical works suggest that the pebble accretion process is important for planet formation in protoplanetary disks, because it accelerates the growth of planetary cores. While several observations reveal axisymmetric sharp gaps in very young disks, which may be indicative of the existence of planets. We investigate the possibility of planet formation via pebble accretion in much earlier phases, the gravitationally unstable disks of class 0/I young stellar objects. We find that under the conditions of the class 0/I disks, the pebble accretion timescales can be shorter compared to the typical protoplanetary disks due to larger gas and dust accretion rate, but also find that the accretion timescale is not always a decreasing function of the gas accretion rate. By using estimated accretion timescales, we give a required initial mass to form cores of gas giants within the lifetime of class 0/I phases under several parameters, such as radial distances from the host star, gas accretion rates, and dust-to-gas mass ratio. In the most optimistic case, for example the dust-to-gas mass ratio is $f=3f_{\rm solar}$, $\sim10^{-4}M_{\oplus}$ objects at 10 au can grow to $10M_{\oplus}$ cores during the typical lifetime of the class 0/I phases, 0.5 Myr.