A Comprehensive View of Circumstellar Disks in Chamaeleon I: Infrared Excess, Accretion Signatures, and Binarity
A Comprehensive View of Circumstellar Disks in Chamaeleon I: Infrared Excess, Accretion Signatures, and Binarity
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Chamaeleon I 中的星周盘的全面视图：红外过剩、吸积特征和二元性
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发表时间：
2007
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通讯作者：
M. V. van Kerkwijk
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作者：
I. Damjanov;R. Jayawardhana;A. Scholz;Mirza Ahmic;D. Nguyen;A. Brandeker;M. V. van Kerkwijk
我们对81颗年轻的低质量恒星和褐矮星周围的盘进行了全面的研究，这些恒星和褐矮星位于附近的~2 Myr老变色龙I恒星形成区。我们使用斯皮策太空望远镜的中红外测光技术，辅以地面高分辨率光学光谱和自适应光学成像的发现。我们根据8 μm和24 μm的颜色过量分别得出了52%±6%和58%的磁盘分数，与其他类似年龄的星团的报告一致。在不确定度范围内，我们在Cha I的K3-M8天体样本中的圆盘频率与恒星质量无关。无磁盘和含磁盘对象具有相似的空间分布。在我们的样本中没有明显的过渡磁盘，这意味着内部磁盘清理过程的时间尺度很快；然而，在3-8 μm处发现了微弱的过量，在24 μm处发现了大量过量，这可能表明颗粒生长和灰尘沉积在内盘。对于35个具有高分辨率光谱的天体的子样本，我们研究了吸积特征和尘埃盘之间的联系：在绝大多数情况下（29/35），两者之间的相关性很好，这表明，平均而言，气体耗散的时间尺度与清除内部尘埃盘的时间尺度相似。例外的是六个天体，它们的尘埃盘似乎持续存在，即使吸积已经停止或下降到可测量的水平以下。65个目标的自适应光学图像显示，17个目标在（投影）距离为10-80天文单位的地方有伴星。在5个小于20 AU的双星中，有4个缺乏红外过剩，这可能表明一个紧密的伴星会导致更快的盘分散。最近的有多余的双星相隔约20天文单位，这为外盘半径设定了约8天文单位的上限。有伴星的恒星的总体圆盘频率（35%）低于总样本的值（但在统计上仍与之一致）。
We present a comprehensive study of disks around 81 young, low-mass stars and brown dwarfs in the nearby ~2 Myr old Chamaeleon I star-forming region. We use mid-infrared photometry from the Spitzer Space Telescope, supplemented by findings from ground-based high-resolution optical spectroscopy and adaptive optics imaging. We derive disk fractions of 52% ± 6% and 58% based on 8 and 24 μm color excesses, respectively, consistent with those reported for other clusters of similar age. Within the uncertainties, the disk frequency in our sample of K3-M8 objects in Cha I does not depend on stellar mass. Diskless and disk-bearing objects have similar spatial distributions. There are no obvious transition disks in our sample, implying a rapid timescale for the inner disk clearing process; however, we find two objects with weak excess at 3-8 μm and substantial excess at 24 μm, which may indicate grain growth and dust settling in the inner disk. For a subsample of 35 objects with high-resolution spectra, we investigate the connection between accretion signatures and dusty disks: in the vast majority of cases (29/35) the two are well correlated, suggesting that, on average, the timescale for gas dissipation is similar to that for clearing the inner dust disk. The exceptions are six objects for which dust disks appear to persist even though accretion has ceased or dropped below measurable levels. Adaptive optics images of 65 of our targets reveal that 17 have companions at (projected) separations of 10-80 AU. Of the five ≲20 AU binaries, four lack infrared excess, possibly indicating that a close companion leads to faster disk dispersal. The closest binary with excess is separated by ~20 AU, which sets an upper limit of ~8 AU for the outer disk radius. The overall disk frequency among stars with companions (35%) is lower than (but still statistically consistent with) the value for the total sample.