76 T dwarfs from the UKIDSS LAS: benchmarks, kinematics and an updated space density
76 T dwarfs from the UKIDSS LAS: benchmarks, kinematics and an updated space density
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来自 UKIDSS LAS 的 76 个 T 矮星：基准、运动学和更新的空间密度
DOI：
10.1093/mnras/stt740
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发表时间：
2013
影响因子：
4.8
通讯作者：
Burningham B
中科院分区：
文献类型：
--
作者：
Burningham B
我们报告了在UKIRT红外深空巡天（UKIDSS）大面积巡天（LAS）中发现的76颗新的T矮星。介绍了新天体的近红外宽带和窄带光度法和光谱学，以及广域红外巡天探测器（WISE）和暖斯皮策光度法。从新的两历元LAS固有运动表中给出了128颗UKIDSS T矮星的固有运动。我们使用这些运动来确定两个新的基准系统：LHS 6176AB， T8p+M4对和HD 118865AB， T5.5+F8对。利用初等星的年龄约束和进化模型来约束半径，我们从它们的放热光度估计了它们的物理性质。我们将已知基准T矮星的颜色和性质与最新模型大气进行了比较，得出了两个主要结论。首先，似乎h−[4.5]和j−W2颜色对金属丰度比以前认识到的更敏感，因此在考虑使用这些颜色的冷物体的相对性质时，金属丰度的差异可能比interff的差异更重要。其次，当使用新的模型网格和扩展后的晚t矮星和基准样本时，先前注意到的晚t矮星样本中年轻天体的明显优势不再明显。在我们提供的简化固有运动图上，晚期T型矮星和早期T型矮星明显相似的分布支持了这一点。最后，我们给出了晚t矮星的更新空间密度，并将我们的值与模拟预测和wise的值进行了比较。
We report the discovery of 76 new T dwarfs from the UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Near-infrared broad- and narrow-band photometry and spectroscopy are presented for the new objects, along withWide-field Infrared Survey Explorer(WISE) and warm-Spitzerphotometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8p+M4 pair and HD 118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii, we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. First, it appears that theH− [4.5] andJ−W2 colours are more sensitive to metallicity than has previously been recognized, such that differences in metallicity may dominate over differences inTeffwhen considering relative properties of cool objects using these colours. Secondly, the previously noted apparent dominance of young objects in the late-T dwarf sample is no longer apparent when using the new model grids and the expanded sample of late-T dwarfs and benchmarks. This is supported by the apparently similar distribution of late-T dwarfs and earlier type T dwarfs on reduced proper motion diagrams that we present. Finally, we present updated space densities for the late-T dwarfs, and compare our values to simulation predictions and those fromWISE.