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arXiv 0910.3539astro-ph.SR
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原行星盘上的Bondi-Hoyle-Lyttleton吸积

Bondi-Hoyle-Lyttleton Accretion onto a Protoplanetary Disk

Nickolas Moeckel, Henry B. Throop

摘要:

年轻的恒星系统在其诞生星团的势能中运行,在恒星诞生和星团气体扩散之间的时期,可以从致密的分子星际介质中吸积。在这段可能跨越数百万年的时间里,吸积的物质数量可以与最初的原行星盘中的数量相媲美; Throop和Bally(2008)最近强调了这种“尾端”吸积对行星形成的潜在重要性。虽然吸积到一个质点是成功地模拟了经典的邦迪-霍伊尔-利特尔顿解决方案,吸积到一个星盘系统的更复杂的情况下,无法解析解。在本文中,我们通过直接的流体动力学模拟研究了致密的星际物质吸积到一个恒星与相关的气体原行星盘。我们讨论的吸积流的结构所造成的磁盘的变化,反之亦然。我们发现,沉浸在一个密集的吸积流可以重新分配磁盘材料,使外盘向内迁移,增加内盘表面密度,减少外半径。吸积流也触发了螺旋密度特征的发展,并改变了盘的倾角。在有和没有圆盘的情况下,恒星的平均吸积率大致相同。我们讨论了这一过程对行星形成的潜在影响,包括引发引力不稳定的可能性;磁盘和恒星之间的倾角差异;以及在引力稳定系统中出现螺旋结构。

英文摘要:

Young stellar systems orbiting in the potential of their birth cluster can accrete from the dense molecular interstellar medium during the period between the star's birth and the dispersal of the cluster's gas. Over this time, which may span several Myr, the amount of material accreted can rival the amount in the initial protoplanetary disk; the potential importance of this `tail-end' accretion for planet formation was recently highlighted by Throop & Bally (2008). While accretion onto a point mass is successfully modeled by the classical Bondi-Hoyle-Lyttleton solutions, the more complicated case of accretion onto a star-disk system defies analytic solution. In this paper we investigate via direct hydrodynamic simulations the accretion of dense interstellar material onto a star with an associated gaseous protoplanetary disk. We discuss the changes to the structure of the accretion flow caused by the disk, and vice versa. We find that immersion in a dense accretion flow can redistribute disk material such that outer disk migrates inwards, increasing the inner disk surface density and reducing the outer radius. The accretion flow also triggers the development of spiral density features, and changes to the disk inclination. The mean accretion rate onto the star remains roughly the same with and without the presence of a disk. We discuss the potential impact of this process on planet formation, including the possibility of triggered gravitational instability; inclination differences between the disk and the star; and the appearance of spiral structure in a gravitationally stable system.

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。

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