In this paper we present an investigation of tidal tails around the old open cluster M 67 using Gaia-DR2. We identify likely extra-tidal stars around M 67 using principal component analysis (PCA) and a Gaussian mixture model (GMM). We find 1618 stars closely related to M 67, 85 of which are likely extra-tidal stars. We find clear evidence for the existence of two well-defined tidal tails emerging from M 67. The tidal tails extend out to projected distances of at least |${2{^{\circ}_{.}}5}$| (∼39 pc), which is more than twice as large as the tidal radius of the cluster. Based on LAMOST-DR5 data, we confirm that 13 extra-tidal stars have radial velocities and metallicities similar to those of the cluster. Furthermore, we also confirm that the extra-tidal stars cover a wide mass range of 0.2–1.1 M_⊙, and nearly half the extra-tidal stars are less than 0.57 M_⊙. The total mass of the extra-tidal stars is determined to be about 55 M_⊙. We estimate a mass-loss rate of ∼2.8 M_⊙ Myr⁻¹ for M 67. Possible origins of these extra-tidal stars are discussed.

中文翻译：

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使用主成分分析法检测疏散星团M 67附近的潮汐尾巴

在本文中，我们使用Gaia-DR2对旧的开放星团M 67周围的潮汐尾巴进行了调查。我们使用主成分分析（PCA）和高斯混合模型（GMM）识别M 67附近的可能潮外星。我们发现1618颗与M 67密切相关的恒星，其中85颗可能是潮外星。我们找到了从M 67出现两个明确定义的潮汐尾巴的明确证据。这些潮汐尾翼延伸到投影距离至少| $ {2 {^ {\ circ} _ {。}} 5} $ |。（〜39 pc），是簇的潮汐半径的两倍多。根据LAMOST-DR5数据，我们确认13个潮外星的径向速度和金属度与星团类似。此外，我们还确认，潮外星的质量范围覆盖0.2-1.1  M_⊙和近一半的额外潮星都小于0.57 中号_⊙。额外的潮星的总质量被确定为约55 中号_⊙。我们估计〜2.8的质量损失率 中号_⊙ 秘耳^-1到这些额外的潮星的M个67.可能的起源进行了讨论。