arXiv 1503.052092015-03-17astro-ph.GAastro-ph.EP

行星和棕矮星周围盘的性质作为盘碎裂的证据

The properties of discs around planets and brown dwarfs as evidence for disc fragmentation

Dimitris Stamatellos, Gregory J. Herczeg

备注：: 10 pages, 8 figures, MNRAS accepted
DOI：: 10.1093/mnras/stv526

摘要：

直接成像搜索揭示了许多非常低质量的物体，包括少量行星质量的物体，作为年轻恒星的宽轨道伴侣。这些物体的形成机制仍然不确定。在本文中，我们提出了预测的光盘碎片模型的属性，这样的低质量物体周围的光盘。我们发现，由类太阳恒星（称为“父”盘和“父”星）承载的盘中的碎片形成的物体周围的盘比从${M}_{\rm disc}-M_*$关系（这是由质量为$M_*>0.2 {\rm M}_{\odot}$的恒星导出的）预期的质量更大。因此，这些天体的吸积速率也高于根据$\dot{M}_*-M_*$关系式所预期的速率。此外，棕矮星或行星的质量与其盘的质量以及从盘到其上的吸积速率之间没有显著的相关性。通过盘碎片形成的物体周围的盘在形成后的最初几个kyr期间从其母恒星的盘吸积气体时，其质量比预期的大。它们吸积的气体量以及它们的质量取决于它们在母盘中的运动方式以及它们与母盘的相互作用方式。观测到的盘质量和吸积速率与盘碎裂模型的预测相一致。未来的观测（例如ALMA）将检验这一模型的预测，这些观测的对象是质量甚至更低的亚恒星物体（年轻行星和年轻的低质量棕矮星），在这些亚恒星物体中，由盘碎裂模型预测的比例关系与为高质量恒星建立的相应关系有很大的差异。

英文摘要：

Direct imaging searches have revealed many very low-mass objects, including a small number of planetary mass objects, as wide-orbit companions to young stars. The formation mechanism of these objects remains uncertain. In this paper we present the predictions of the disc fragmentation model regarding the properties of the discs around such low-mass objects. We find that the discs around objects that have formed by fragmentation in discs hosted by Sun-like stars (referred to as 'parent' discs and 'parent' stars) are more massive than expected from the ${M}_{\rm disc}-M_*$ relation (which is derived for stars with masses $M_*>0.2 {\rm M}_{\odot}$). Accordingly, the accretion rates onto these objects are also higher than expected from the $\dot{M}_*-M_*$ relation. Moreover there is no significant correlation between the mass of the brown dwarf or planet with the mass of its disc nor with the accretion rate from the disc onto it. The discs around objects that form by disc fragmentation have larger than expected masses as they accrete gas from the disc of their parent star during the first few kyr after they form. The amount of gas that they accrete and therefore their mass depend on how they move in their parent disc and how they interact with it. Observations of disc masses and accretion rates onto very low-mass objects are consistent with the predictions of the disc fragmentation model. Future observations (e.g. by ALMA) of disc masses and accretion rates onto substellar objects that have even lower masses (young planets and young, low-mass brown dwarfs), where the scaling relations predicted by the disc fragmentation model diverge significantly from the corresponding relations established for higher-mass stars, will test the predictions of this model.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

相关论文