We have conducted a kinematic study of 165 young M dwarfs with ages of 300?Myr. Our sample is composed of stars and brown dwarfs with spectral types ranging from K7 to L0, detected by ROSAT and with photometric distances of 25?pc assuming that the stars are single and on the main sequence. In order to find stars kinematically linked to known young moving groups (YMGs), we measured radial velocities for the complete sample with Keck and CFHT optical spectroscopy and trigonometric parallaxes for 75 of the M dwarfs with the CAPSCam instrument on the du Pont 2.5?m Telescope. Due to their youthful overluminosity and unresolved binarity, the original photometric distances for our sample underestimated the distances by 70% on average, excluding two extremely young (3?Myr) objects found to have distances beyond a few hundred parsecs. We searched for kinematic matches to 14 reported YMGs and identified 10 new members of the AB Dor YMG and 2 of the Ursa Majoris group. Additional possible candidates include six Castor, four Ursa Majoris, two AB Dor members, and one member each of the Her-Lyr and β Pic groups. Our sample also contains 27 young low-mass stars and 4 brown dwarfs with ages 150?Myr that are not associated with any known YMG. We identified an additional 15 stars that are kinematic matches to one of the YMGs, but the ages from spectroscopic diagnostics and/or the positions on the sky do not match. These warn against grouping stars together based only on kinematics and that a confluence of evidence is required to claim that a group of stars originated from the same star-forming event.
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机译：我们对165个年龄在300？Myr的M小矮人进行了运动学研究。我们的样本由恒星和褐矮星组成，光谱类型从K7到L0，由ROSAT检测到，假设恒星是单星且位于主序列上，其光度距离为25？pc。为了找到与已知的年轻运动群（YMG）运动学相关的恒星，我们使用凯克（Keck）和CFHT光谱仪测量了整个样本的径向速度，并使用位于杜邦2.5？m上的CAPSCam仪器测量了75个M矮星的三角视差。望远镜。由于它们年轻的发光度和未解决的二值性，我们样本的原始光度距离平均低了70％，不包括两个发现的极年轻（3？Myr）物体的距离超过几百秒差距。我们搜索了14个报告的YMG的运动学匹配，并确定了AB Dor YMG的10个新成员和Ursa Majoris组的2个。其他可能的候选者包括6个Castor，4个Ursa Majoris，2个AB Dor成员以及Her-Lyr和βPic组各一个。我们的样本还包含27个年轻的低质量恒星和4个150迈尔的褐矮星，它们与任何已知的YMG都不相关。我们确定了另外15个恒星，它们与其中一个YMG运动匹配，但是光谱诊断的年龄和/或天空位置不匹配。他们警告不要仅根据运动学将恒星聚集在一起，并且需要有大量证据来证明一群恒星起源于同一恒星形成事件。
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