The minimum Jeans mass, brown dwarf companion IMF, and predictions for detection of Y-type dwarfs
The minimum Jeans mass, brown dwarf companion IMF, and predictions for detection of Y-type dwarfs
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最小 Jeans 质量、棕矮星伴星 IMF 以及 Y 型矮星探测预测
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
I. Song
中科院分区：
文献类型：
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作者：
B. Zuckerman;I. Song
冷的L型和T型天体分别在1988年和1995年作为恒星的伴星被首次发现。更冷的Y型光谱类别（Teff < 500 K）的某个例子还没有看到。最近对恒星和褐矮星的红外成像观测表明，具有大半长轴和质量小于褐矮星/巨行星分界线（13.5兆焦耳）的亚恒星伴星是罕见的。分子云的Jeans质量碎裂的理论考虑与这个最小质量截止值一致，也与最低质量成像同伴的半长轴（数百个Au）特征一致。因此，具有大半长轴的Y类伴星在年龄小于2 Gyr的恒星周围应该是稀少的，在所有年龄的亚恒星主恒星周围也是如此。通过关注年轻恒星主星的褐矮星伴星，可以推导出整个褐矮星质量范围内（13兆焦至79兆焦）的褐矮星IMF的第一个估计值--褐矮星伴星的数量与质量成正比-1.2 ± 0。2 P电源。
Cool L- and T-type objects were discovered first as companions to stars in 1988 and 1995, respectively. A certain example of the even cooler Y-type spectral class (Teff < 500 K) has not been seen. Recent infrared-imaging observations of stars and brown dwarfs indicate that substellar companions with large semi-major axes and with masses less than the brown dwarf/giant planet dividing line (∼13.5 MJ) are rare. Theoretical considerations of the Jeans mass fragmentation of molecular clouds are consistent with this minimum mass cutoff and also with the semi-major axis (hundreds of AU) characteristic of the lowest mass imaged companions. As a consequence, Y-class companions with large semi-major axes should be scarce around stars <2 Gyr old, and also around substellar primaries of all ages. By focusing on brown dwarf companions to young stellar primaries, it is possible to derive a first estimate of the brown dwarf IMF over the entire range of brown dwarf masses (13 MJ to 79 MJ) – the number of companion brown dwarfs is proportional to the mass to the −1.2 ± 0. 2p ower.