A Volume-limited Sample of Ultracool Dwarfs. I. Construction, Space Density, and a Gap in the L/T Transition
A Volume-limited Sample of Ultracool Dwarfs. I. Construction, Space Density, and a Gap in the L/T Transition
复制标题
超冷矮星的体积有限的样本。
作者：
W. Best;Michael C. Liu;E. Magnier;T. Dupuy
我们提出了一个新的体积有限的样本L0-T8矮星到25 pc完全定义的松弛，使用我们最近的测量从UKIRT/WFCAM沿着与盖亚DR 2和文献松弛。我们的样本有369个成员，是迄今为止L和T矮星中最大的L-lax定义的体积有限样本，为此类天体提供了最精确的空间密度。我们发现当地的L0-T8矮星人口包括年轻的对象（10.2亿年）和次矮星，从最近的研究有利于代表年龄10.4亿年的ultracool现场人口的预期。这也是第一个全面绘制从L到T矮星（光谱类型为L 8-T4）过渡的体积有限的样本。在去除二进制后，我们在L/T过渡中识别出一个先前未识别的、统计上显著（>4.4σ）的颜色宽度为1.5 mag的间隙，即，在我们有限的样本中缺乏这样的物体，这意味着大气演化的快速阶段。相比之下，迄今为止最成功的L/T转换模型-Saumon & Marley的“混合”模型-预测了相同颜色的物体堆积，我们发现了缺陷，展示了模拟冷却棕矮星大气的挑战。我们的样本说明了来自Vera Rubin Obsevatory即将进行的空间和时间遗产调查的更大样本的见解。
We present a new volume-limited sample of L0–T8 dwarfs out to 25 pc defined entirely by parallaxes, using our recent measurements from UKIRT/WFCAM along with Gaia DR2 and literature parallaxes. With 369 members, our sample is the largest parallax-defined volume-limited sample of L and T dwarfs to date, yielding the most precise space densities for such objects. We find the local L0–T8 dwarf population includes young objects (≲200 Myr) and subdwarfs, as expected from recent studies favoring representative ages ≲4 Gyr for the ultracool field population. This is also the first volume-limited sample to comprehensively map the transition from L to T dwarfs (spectral types ≈L8–T4). After removing binaries, we identify a previously unrecognized, statistically significant (>4.4σ) gap ≈0.5 mag wide in colors in the L/T transition, i.e., a lack of such objects in our volume-limited sample, implying a rapid phase of atmospheric evolution. In contrast, the most successful models of the L/T transition to date—the “hybrid” models of Saumon & Marley—predict a pileup of objects at the same colors where we find a deficit, demonstrating the challenge of modeling the atmospheres of cooling brown dwarfs. Our sample illustrates the insights to come from even larger parallax-selected samples from the upcoming Legacy Survey of Space and Time by the Vera Rubin Obsevatory.
DOI：
10.3847/1538-4365/aaf6af
发表时间：
2018-12
期刊：
The Astrophysical Journal Supplement Series
影响因子：
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作者：
J. Kirkpatrick;E. Martin;R. Smart;Alfred J. Cayago;C. Beichman;F. Marocco;C. Gelino;J. Faherty-
通讯作者：
J. Kirkpatrick;E. Martin;R. Smart;Alfred J. Cayago;C. Beichman;F. Marocco;C. Gelino;J. Faherty-