哈勃空间望远镜对银河系高纬度超冷矮星的观测
Hubble Space Telescope Observations of Field Ultracool Dwarfs at High Galactic Latitude
摘要：
我们提供了一个新发现的17个晚于M8的超冷矮星候选者的样本，来自{ \it哈勃太空望远镜}宽视场相机3红外成像的231.90 arcmin 2。通过比较17.5<J_125<25.5 AB星等的观测数与指数盘模型，我们估计了对于f_b=0的二元分数，垂直标度高度z_scl=290 +- 25（随机）+- 30（系统）pc。虽然我们的估计与已发表的结果大致一致，但我们认为这些差异可以归因于样本的性质，目前的样本包含的亚恒星天体比以前的工作要多得多。我们预测，由于盘边缘的数密度呈指数下降，天体计数应在J_{125} ~24 AB等处达到峰值。最后，我们认为，在规模的高度与光谱类型的趋势可能会崩溃的棕矮星，因为他们不解决的主要序列。
英文摘要：
We present a sample of 17 newly discovered ultracool dwarf candidates later than ~M8, drawn from 231.90 arcmin2 of {\it Hubble Space Telescope} Wide Field Camera 3 infrared imaging. By comparing the observed number counts for 17.5<J_125<25.5 AB mag to an exponential disk model, we estimate a vertical scale height of z_scl=290 +- 25 (random) +- 30 (systematic) pc for a binarity fraction of f_b=0. While our estimate is roughly consistent with published results, we suggest that the differences can be attributed to sample properties, with the present sample containing far more substellar objects than previous work. We predict the object counts should peak at J_{125}~24 AB mag due to the exponentially-declining number density at the edge of the disc. We conclude by arguing that trend in scale height with spectral type may breakdown for brown dwarfs since they do not settle onto the main sequence.
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