Triggered O Star Formation in M20 via Cloud–Cloud Collision: Comparisons between High-resolution CO Observations and Simulations

Torii, Kazufumi; Hattori, Yusuke; Hasegawa, Keisuke; Ohama, Akio; Haworth, Thomas J.; Shima, K; Habe, A.; Tachihara, Kengo; Mizuno, N.; Onishi, Toshikazu; Mizuno, Akira; Fukui, Y.

doi:10.3847/1538-4357/835/2/142

Cited by 104 publications

(148 citation statements)

References 36 publications

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“…Observations have shown that there is a possible relation between cloud-cloud collision and massive star formation (Furukawa et al 2009;Fukui et al 2014Fukui et al , 2016Ohama et al 2010;Torii et al 2011Torii et al , 2015Torii et al , 2017. Two super star clusters Westerland and NGC 3603 (Furukawa et al 2009;Fukui et al 2014;Ohama et al 2010) and the Triffid Nebula (Torii et al 2011) show relative velocity between 10 and 20 km/s under molecular lines observations.…”

Section: Introductionmentioning

confidence: 99%

Collision between molecular clouds – I. The effect of the cloud virial ratio in head-on collisions

Tanvir

Dale

2020

Monthly Notices of the Royal Astronomical Society

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In a series of papers we investigate the effect of collisions between turbulent molecular clouds on their structure, evolution and star formation activity. In this paper we look into the role of the clouds' initial virial ratios. Three different scenarios were examined: both clouds initially bound, one cloud bound and one unbound, and both clouds initially unbound. Models in which one or both clouds are bound generate filamentary structures aligned along the collision axis and discernible in position-position and position-velocity space. If neither cloud is bound, no filaments result. Unlike in previous simulations of collisions between smooth clouds, owing to the substructure created in the clouds by turbulence before the collisions, dissipation of kinetic energy by the collision is very inefficient and in none of our simulations is sufficient bulk kinetic energy lost to render the clouds bound. Simulations where both clouds are bound created twice as much stellar mass than the bound-unbound model, and both these scenarios produced much more stellar mass than the simulation in which both clouds are unbound. Each simulation was also compared with a control run in which the clouds do not collide. We find the bound-bound collision increases the overall star formation efficiency by a factor of approximately two relative to the control, but that the bound-unbound collision produces a much smaller increase, and the collision has very little effect on the unbound-unbound cloud collision.

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Section: Introductionmentioning

confidence: 99%

Collision between molecular clouds – I. The effect of the cloud virial ratio in head-on collisions

Tanvir

Dale

2020

Monthly Notices of the Royal Astronomical Society

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“…which is the emission between two velocity peaks with intermediate intensities (e.g., Torii et al in prep. ;Torii et al 2017a;Haworth et al 2015a;Haworth et al 2015b). The turbulent gas is replenished as long as the collision continues.…”

Section: The Cloud-cloud Collision Modelmentioning

confidence: 99%

“…Another observational signature of cloud-cloud collisions is complementary distribution between two velocity clouds" Torii et al 2017a). For an observer viewing angle parallel to the collisional axis so that the two clouds are spatially coincident, the observer can see an anti-correlated or complementary distribution between the two clouds separated in velocity, as the larger cloud with a cavity displays a ring-like gas distribution on the sky.…”

Section: The Cloud-cloud Collision Modelmentioning

confidence: 99%

“…Additional possible cases of multiple O star formation triggered by a cloud-cloud collision are reported for M42 , NGC 6334-NGC 6357 (Fukui et al 2017c), M17 (Nishimura et al 2017a), W49A (Miyawaki et al 1986, 2009, Buckley & Ward-Thompson 1996, W51 (Okumura et al 2001;Kang et al 2010 ;Fujita et al in preperation) and R136 (Fukui et al 2017a). In addition to above, many star forming regions and dense clumps in the Milky Way have been suggested to be triggered by a cloud-cloud collision, LkHα198 (Loren 1977); IRAS 19550+3248 (Koo et al 1994); IRAS 2306+1451 (Vallee 1995); M20 (Torii et al 2011(Torii et al , 2017a; RCW120 (Torii et al 2015); N37 (Baug et al 2016); GM 24 (Fukui et al 2017d); M16 (Nishimura et al 2017b); RCW34 (Hayashi et al 2017); RCW36 (Sano et al 2017a); RCW166 (Ohama et al 2017a); S116, S117, S118 (Fukui et al 2017e); RCW79 (Ohama et al 2017c); Sh2-48 (Torii et al 2017); NGC 2024 (Ohama et al 2017b); NGC 2068, NGC 2071 (Tsutsumi et al 2017); NGC 2359 (Sano et al 2017b); S87 (Xue & Wu 2008); S87E, S88B, AFGL 5142, AFGL 5180 (Higuchi et al 2010); G0.253+0.016 (Higuchi et al 2014); Circinus-E cloud (Shimoikura & Dobashi 2011); Sh2-252 (Shimoikura et al 2013);L1641-N (Nakamura et al 2012; Serpens Main Cluster (Duarte-Cabral et al 2011); Serpens South (Nakamura et al 2014); L1004E in the Cygnus OB 7 (Dobashi et al 2014); G35.20-0.74 (Dewan...…”

Section: Cloud-cloud Collisions As a Trigger Of High-mass Star Formationmentioning

confidence: 99%

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FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN): Molecular clouds toward W 33; possible evidence for a cloud–cloud collision triggering O star formation

Kohno

Torii

Tachihara

et al. 2018

Publications of the Astronomical Society of Japan

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We observed molecular clouds in the W33 high-mass star-forming region associated with compact and extended H II regions using the NANTEN2 telescope as well as the Nobeyama 45-m telescope in the J =1-0 transitions of 12 CO, 13 CO, and C 18 O as a part of the FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) legacy survey. We detected three velocity components at 35 km s −1 , 45 km s −1 , and 58 km s −1 . The 35 km s −1 and 58 km s −1 clouds are likely to be physically associated with W33 because of the enhanced 12 CO J = 3-2 to J =1-0 intensity ratio as R 3−2/1−0 > 1.0 due to the ultraviolet irradiation by OB stars, and morphological correspondence between the distributions of molecular gas and the infrared and radio continuum emissions excited by high-mass stars. The two clouds show complementary distributions around W33. The velocity separation is too large to be gravitationally bound, and yet not explained by expanding motion by stellar feedback. c 2014. Astronomical Society of Japan. 2Publications of the Astronomical Society of Japan, (2014), Vol. 00, No. 0 Therefore, we discuss that a cloud-cloud collision scenario likely explains the high-mass star formation in W33.

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“…Instead, in the following sections, we focus on a cloud-cloud collision, which has been suggested as a triggering mechanism of massive star formation (e.g. Habe & Ohta 1992;Furukawa et al 2009;Ohama et al 2010;Fukui et al 2014Fukui et al , 2016Fukui et al , 2018Torii et al 2017), and look for the cause of the lack of massive stars in strong bars.…”

Section: Cloud Propertiesmentioning

confidence: 99%

Fast cloud–cloud collisions in a strongly barred galaxy: suppression of massive star formation

Fujimoto

Maeda

Habe

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Recent galaxy observations show that star formation activity changes depending on galactic environments. In order to understand the diversity of galactic-scale star formation, it is crucial to understand the formation and evolution of giant molecular clouds in an extreme environment. We focus on observational evidence that bars in strongly barred galaxies lack massive stars even though quantities of molecular gas are sufficient to form stars. In this paper, we present a hydrodynamical simulation of a strongly barred galaxy, using a stellar potential which is taken from observational results of NGC1300, and we compare cloud properties between different galactic environments: bar, bar-end and spiral arms. We find that the mean of cloud's virial parameter is α vir ∼ 1 and that there is no environmental dependence, indicating that the gravitationally-bound state of a cloud is not behind the observational evidence of the lack of massive stars in strong bars. Instead, we focus on cloud-cloud collisions, which have been proposed as a triggering mechanism for massive star formation. We find that the collision speed in the bar is faster than those in the other regions. We examine the collision frequency using clouds' kinematics and conclude that the fast collisions in the bar could originate from random-like motion of clouds due to elliptical gas orbits shifted by the bar potential. These results suggest that the observed regions of lack of active star-formation in the strong bar originate from the fast cloudcloud collisions, which are inefficient in forming massive stars, due to the galactic-scale violent gas motion.

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Triggered O Star Formation in M20 via Cloud–Cloud Collision: Comparisons between High-resolution CO Observations and Simulations

Cited by 104 publications

References 36 publications

Collision between molecular clouds – I. The effect of the cloud virial ratio in head-on collisions

Collision between molecular clouds – I. The effect of the cloud virial ratio in head-on collisions

FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN): Molecular clouds toward W 33; possible evidence for a cloud–cloud collision triggering O star formation

Fast cloud–cloud collisions in a strongly barred galaxy: suppression of massive star formation

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