MOLECULAR CLOUDS IN THE TRIFID NEBULA M20: POSSIBLE EVIDENCE FOR A CLOUD–CLOUD COLLISION IN TRIGGERING THE FORMATION OF THE FIRST GENERATION STARS
MOLECULAR CLOUDS IN THE TRIFID NEBULA M20: POSSIBLE EVIDENCE FOR A CLOUD–CLOUD COLLISION IN TRIGGERING THE FORMATION OF THE FIRST GENERATION STARS
复制标题
DOI：
10.1088/0004-637x/738/1/46
复制
发表时间：
2011-06
期刊：
影响因子：
--
通讯作者：
K. Torii;R. Enokiya;H. Sano;S. Yoshiike;N. Hanaoka;A. Ohama;N. Furukawa;J. Dawson;N. Moribe;K. Oishi;Y. Nakashima;T. Okuda;H. Yamamoto;A. Kawamura;N. Mizuno;H. Maezawa;T. Onishi;A. Mizuno;Y. Fukui
中科院分区：
文献类型：
--
作者：
K. Torii;R. Enokiya;H. Sano;S. Yoshiike;N. Hanaoka;A. Ohama;N. Furukawa;J. Dawson;N. Moribe;K. Oishi;Y. Nakashima;T. Okuda;H. Yamamoto;A. Kawamura;N. Mizuno;H. Maezawa;T. Onishi;A. Mizuno;Y. Fukui
在 12CO 和 13CO 的 J = 2–1 和 J = 1–0 跃迁中对三裂星云 M20 的分子云进行了大规模研究。 M20 主要被 O7.5 星 HD164492 电离。研究表明，有两种分子成分以不同的速度在 M20 中心达到峰值，并且它们的温度（通过大速度梯度分析得出的 30-50 K）明显高于周围环境的 10 K。我们将这两个云确定为M20中第一代恒星的母云。每个云的质量估计为~103 M☉，它们的分离速度为~8 km s−1，超过~1-2 pc。我们发现 M20 中恒星和分子气体的总质量小于 ∼3.2 × 103 M☉，这个数量级太小，不足以通过引力束缚该系统。我们认为，第一代恒星（包括主电离 O7.5 恒星）的形成是由两个云在 ∼1 Myr 的短时间尺度内发生碰撞而触发的，这是与 Westerlund 2 一起的第二个例子，其中超级星团可能是由于云与云碰撞触发而形成的。
A large-scale study of the molecular clouds toward the Trifid Nebula, M20, has been made in the J = 2–1 and J = 1–0 transitions of 12CO and 13CO. M20 is ionized predominantly by an O7.5 star HD164492. The study has revealed that there are two molecular components at separate velocities peaked toward the center of M20 and that their temperatures—30–50 K as derived by a large velocity gradient analysis—are significantly higher than the 10 K of their surroundings. We identify the two clouds as the parent clouds of the first generation stars in M20. The mass of each cloud is estimated to be ∼103 M☉ and their separation velocity is ∼8 km s−1 over ∼1–2 pc. We find that the total mass of stars and molecular gas in M20 is less than ∼3.2 × 103 M☉, which is too small by an order of magnitude to gravitationally bind the system. We argue that the formation of the first generation stars, including the main ionizing O7.5 star, was triggered by the collision between the two clouds in a short timescale of ∼1 Myr, a second example alongside Westerlund 2, where a super-star cluster may have been formed due to cloud–cloud collision triggering.