论文标题
NICMOS内核相干涉指标II：附近的棕色矮人的人口统计
NICMOS Kernel-Phase Interferometry II: Demographics of Nearby Brown Dwarfs
论文作者
论文摘要
星形理论一直在努力再现二进制棕色矮人人口人群（频率，分离，质量比例）。内核相干涉仪对无法访问的经典成像的分离敏感，从而使在氢燃烧极限以下的新物理尺度下进行形成测试。我们从以前对棕色斑点的档案HST/NICMOS调查的内核相分析中分析了检测和灵敏度限制。在使用Gaia距离和进化模型估算了105个晚期M到T矮人的物理性质之后，我们使用贝叶斯框架将这些结果与通过对数正态分离和幂律质量分布定义的模型伴侣种群进行比较。纠正Malmquist偏见时，我们发现$ f = 0.11^{+0.04} _ { - 0.03} $的伴随分数和以$ρ= 2.2^{+1.2} _ { - 1.2} _ { - 1.0} $ au，比以前的研究更小，更紧密。我们还找到了一个强烈有利于相等质量系统的质量比率幂律索引：$γ= 4.0^{+1.7} _ { - 1.5} -11^{+4} _ { - 3} $，取决于现场人群的假定年龄（$ 0.9-3.1 $ gyr）。我们将值的变化归因于我们对内核 - 相干干涉法的使用，这使我们能够解决半轴轴分布的峰值，对低质量伴侣具有显着敏感性。我们证实了先前看到的二元分数随质量降低的趋势，并且在野外年龄亚赛季中对紧密质量系统的强烈偏爱； $ 0.9^{+1.1} _ { - 0.6} $％的系统宽于20 au，$ <1.0^{+1.4} _ { - 0.6} $％的系统具有质量比率$ q <0.6 $。我们将其归因于湍流的碎片设置初始条件，然后是短暂的动态演化时期，在出生群集溶解之前消除了最宽和最低的质量伴侣。
Star formation theories have struggled to reproduce binary brown dwarf population demographics (frequency, separation, mass-ratio). Kernel-phase interferometry is sensitive to companions at separations inaccessible to classical imaging, enabling tests of formation at new physical scales below the hydrogen burning limit. We analyze the detections and sensitivity limits from our previous kernel-phase analysis of archival HST/NICMOS surveys of field brown dwarfs. After estimating physical properties of the 105 late M to T dwarfs using Gaia distances and evolutionary models, we use a Bayesian framework to compare these results to a model companion population defined by log-normal separation and power-law mass-ratio distributions. When correcting for Malmquist bias, we find a companion fraction of $F=0.11^{+0.04}_{-0.03}$ and a separation distribution centered at $ρ=2.2^{+1.2}_{-1.0}$ au, smaller and tighter than seen in previous studies. We also find a mass-ratio power-law index which strongly favors equal-mass systems: $γ=4.0^{+1.7}_{-1.5}-11^{+4}_{-3}$ depending on the assumed age of the field population ($0.9-3.1$ Gyr). We attribute the change in values to our use of kernel-phase interferometry which enables us to resolve the peak of the semimajor axis distribution with significant sensitivity to low-mass companions. We confirm the previously-seen trends of decreasing binary fraction with decreasing mass and a strong preference for tight and equal-mass systems in the field-age sub-stellar regime; only $0.9^{+1.1}_{-0.6}$ % of systems are wider than 20 au and $<1.0^{+1.4}_{-0.6}$% of systems have a mass-ratio $q<0.6$. We attribute this to turbulent fragmentation setting the initial conditions followed by a brief period of dynamical evolution, removing the widest and lowest-mass companions, before the birth cluster dissolves.
