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arXiv 1706.01464astro-ph.GA
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利用金牛座-御夫座双星的二进制统计来区分褐矮星的形成过程

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

M. Marks, E. L. Martín, V. J. S. Béjar, N. Lodieu, P. Kroupa, M. E. Manjavacas, I. Thies, R. Rebolo López, S. Velasco

备注：
accepted for publication in A&A, 11 pages, 4 figures, 1 table
发表信息：
A&A 605, A11 (2017)
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摘要：

BD是通过引力坍缩（“类星”）形成恒星，还是BD和一些质量很低的恒星组成一个独立的群体，与恒星一起形成类似于行星的群体，例如通过星周盘（“外围”）碎裂，是恒星形成问题的关键问题之一。对于金牛座-御夫座的年轻恒星，双星比例很大，对主质量的依赖性很小，大于~0.2Msun，而对于BD，它小于10%。我们调查的情况下，在金牛座的BD形成占主导地位，通过周边碎片。的下降的二进制频率之间的过渡区的恒星和周边形成的建模。采用了一个动力学的星族合成模型，其中双星的形成是普遍的。外围物体分别形成在拱星盘具有独特的初始质量函数（IMF），自己的轨道参数分布的二进制和低的二进制分数。少量的恒星成分的动力学处理占适当的低密度金牛座御夫座嵌入式集群。双星分数下降强烈的质量之间的限制，恒星状和周边形成。特征的位置和陡度取决于这些质量限制。这种趋势可能是唯一的低密度地区托管动态未经处理的二进制人口。在金牛座-御夫座恒星形成区的BD和VLMS双星的未来调查中，二元分数-初级质量图中存在强烈的下降将成为可验证的。这是一个测试的（非）连续性的恒星形成沿质量尺度，分离的恒星和BD人口和占主导地位的形成渠道BD和BD二进制在低恒星密度的地区托管动态未处理的人口。

英文摘要：

Whether BDs form as stars through gravitational collapse ("star-like") or BDs and some very low-mass stars constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk ("peripheral") fragmentation, is one of the key questions of the star-formation problem. For young stars in Taurus-Auriga the binary fraction is large with little dependence on primary mass above ~0.2Msun, while for BDs it is <10%. We investigate a case in which BDs in Taurus formed dominantly through peripheral fragmentation. The decline of the binary frequency in the transition region between star-like and peripheral formation is modelled. A dynamical population synthesis model is employed in which stellar binary formation is universal. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), own orbital parameter distributions for binaries and a low binary fraction. A small amount of dynamical processing of the stellar component is accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. The binary fraction declines strongly between the mass-limits for star-like and peripheral formation. The location of characteristic features and the steepness depend on these mass-limits. Such a trend might be unique to low density regions hosting dynamically unprocessed binary populations. The existence of a strong decline in the binary fraction -- primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is a test of the (non-)continuity of star formation along the mass-scale, the separateness of the stellar and BD populations and the dominant formation channel for BDs and BD binaries in regions of low stellar density hosting dynamically unprocessed populations.

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