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Molecular clouds in the trifid nebula M20: Possible evidence for a cloud-cloud collision in triggering the formation of the first generation stars

Citation

Torii, K and Enokiya, R and Sano, H and Yoshiike, S and Hanaoka, N and Ohama, A and Furukawa, N and Dawson, JR and Moribe, N and Oishi, K and Nakashima, Y and Okuda, T and Yamamoto, H and Kawamura, A and Mizuno, N and Maezawa, H and Onishi, T and Mizuno, A and Fukui, Y, Molecular clouds in the trifid nebula M20: Possible evidence for a cloud-cloud collision in triggering the formation of the first generation stars, The Astrophysical Journal: An International Review of Astronomy and Astronomical Physics, 738, (1) Article 46. ISSN 0004-637X (2011) [Refereed Article]


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Copyright 2011 The American Astronomical Society.

DOI: doi:10.1088/0004-637X/738/1/46

Abstract

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¡ª30-50 K as derived by a large velocity gradient analysis¡ªare 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¨C1 over ~1-2 pc. We find that the total mass of stars and molecular gas in M20 is less than ~3.2 ¡Á 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.

Item Details

Item Type:Refereed Article
Keywords:ISM: clouds; open clusters and associations: individual (M20); radio lines: ISM
Research Division:Physical Sciences
Research Group:Astronomical and Space Sciences
Research Field:Galactic Astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Physical Sciences
Author:Dawson, JR (Dr Joanne Dawson)
ID Code:75006
Year Published:2011
Funding Support:Australian Research Council (FS100100037)
Web of Science® Times Cited:36
Deposited By:Mathematics and Physics
Deposited On:2011-12-23
Last Modified:2017-10-06
Downloads:0

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