RCW 36 in the Vela Molecular Ridge: Evidence for a high-mass star cluster formation triggered by Cloud-Cloud Collision

Abstract

A collision between two molecular clouds is one possible candidate for high-mass star formation. The HII region RCW 36, located in the Vela molecular ridge, contains a young star cluster with two O-type stars. We present new CO observations of RCW 36 with NANTEN2, Mopra, and ASTE using ${}^{12}$CO($J$ = 1-0, 2-1, 3-2) and ${}^{13}$CO($J$ = 2-1) line emissions. We have discovered two molecular clouds lying at the velocities $V_{\mathrm{LSR}}\sim$5.5 and 9 km s${}^{-1}$. Both clouds are likely to be physically associated with the star cluster, as verified by the good spatial correspondence among the two clouds, infrared filaments, and the star cluster. We also found a high intensity ratio of $\sim$0.6-1.2 for CO $J$ = 3-2 / 1-0 toward both clouds, indicating that the gas temperature has been increased due to heating by the O-type stars. We propose that the O-type stars in RCW 36 were formed by a collision between the two clouds, with a relative velocity separation of 5 km s${}^{-1}$. The complementary spatial distributions and the velocity separation of the two clouds are in good agreement with observational signatures expected for O-type star formation triggered by a cloud-cloud collision. We also found a displacement between the complementary spatial distributions of the two clouds, which we estimate to be 0.3 pc assuming the collision angle to be 45${}^{\circ }$ relative to the line-of-sight. We estimate the collision timescale to be $\sim$10${}^5$ yr. It is probable that the cluster age by Ellerbroek et al. (2013b) is dominated by the low-mass members which were not formed under the triggering by cloud-cloud collision, and that the O-type stars in the center of the cluster are explained by the collisional triggering independently from the low-mass star formation.

arXiv comment13 pages, 9 figures, and 2 tables, accepted for publication in PASJ

References in corpus (26)

• Toward Understanding Massive Star Formation
• The COMPLETE Survey of Star-Forming Regions: Phase I Data
• Filaments and ridges in Vela C revealed by Herschel: from low-mass to high-mass star-forming sites
• Formation of Massive Molecular Cloud Cores by Cloud-cloud Collision
• Do cloud-cloud collisions trigger high-mass star formation? I. Small cloud collisions
• Molecular clouds towards RCW 49 and Westerlund 2; Evidence for cluster formation triggered by cloud-cloud collision
• Molecular Clouds Toward the Super Star Cluster NGC3603; Possible Evidence for a Cloud-Cloud Collision in Triggering the Cluster Formation
• Revealing the physical properties of molecular gas in Orion with a large scale survey in J=2-1 lines of 12CO, 13CO and C18O
• Cloud-cloud collision as a trigger of the high-mass star formation; a molecular line study in RCW120
• The two molecular clouds in RCW 38; evidence for formation of the youngest super star cluster in the Milky Way triggered by cloud-cloud collision
• Temperature and Density Distribution in the Molecular Gas Toward Westerlund 2: Further Evidence for Physical Association
• Molecular clouds in the Trifid nebula M20; Possible evidence for a cloud-cloud collision in triggering the formation of the first generation stars
• The Mopra Southern Galactic Plane CO Survey
• Evidence for an inner molecular disk around massive Young Stellar Objects
• VLT K-band spectroscopy of massive young stellar objects in (ultra-)compact HII regions
• VLT K-band spectroscopy of massive stars deeply embedded in IRAS sources with UCHII colours
• Near-IR integral field spectroscopy of ionizing stars and young stellar objects on the borders of HII regions
• The outflow history of two Herbig-Haro jets in RCW 36: HH 1042 and HH 1043
• The Herschel view of the on-going star formation in the Vela-C molecular cloud
• RCW36: characterizing the outcome of massive star formation
• Kinematic Structure of Molecular Gas around High-mass Star YSO, Papillon Nebula, in N159 East in the Large Magellanic Cloud
• ISM gas studies towards the TeV PWN HESS J1825-137 and northern region
• HI, CO, and Dust in the Perseus Cloud
• Deep Near Infrared Imaging toward Vela Molecular Ridge C - 1: A Remarkable Embedded Cluster in RCW 36 -
• The Intermediate-mass Young Stellar Object 08576nr292: Discovery of a disk-jet system
• Tracing H2 column density with atomic carbon (CI) and CO isotopologues

Cited by in corpus (34)

• Unifying low and high mass star formation through density amplified hubs of filaments
• Cloud-cloud collisions and triggered star formation
• An ALMA view of molecular filaments in the Large Magellanic Cloud II: An early stage of high-mass star formation embedded at colliding clouds in N159W-South
• Cloud-cloud collisions in the common foot point of molecular loops 1 and 2 in the Galactic Center
• Formation of the active star forming region LHA 120-N 44 triggered by tidally-driven colliding HI flows
• The Mopra Southern Galactic Plane CO Survey - Data Release 3
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) 2: Possible evidence for formation of NGC~6618 cluster in M17 by cloud-cloud collision
• High-mass star formation possibly triggered by cloud-cloud collision in the HII region RCW 34
• Molecular clouds in the NGC 6334 and NGC 6357 region; Evidence for a 100 pc-scale cloud-cloud collision triggering the Galactic mini-starbursts
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45-m telescope (FUGIN) : Molecular clouds toward W33 ; possible evidence for a cloud-cloud collision triggering O star formation
• Formation of the young compact cluster GM 24 triggered by a cloud-cloud collision
• High-mass star formation in Orion B triggered by cloud-cloud collision: Merging molecular clouds in NGC 2024
• Star Formation Induced by Cloud-Cloud Collisions and Galactic Giant Molecular Cloud Evolution
• FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN). VI. Dense gas and mini-starbursts in the W43 giant molecular cloud complex
• ALMA CO Observations of a Giant Molecular Cloud in M33: Evidence for High-Mass Star Formation Triggered by Cloud-Cloud Collisions
• The SOFIA FEEDBACK Legacy Survey: Dynamics and mass ejection in the bipolar HII region RCW 36
• Cloud-Cloud Collision Induced Star Formation in IRAS 18223-1243
• The formation of a Spitzer bubble RCW79 triggered by cloud-cloud collision
• Dense cores and star formation in the giant molecular cloud Vela~C
• Molecular gas in a Spitzer bubble N4: possible evidence for cloud-cloud collisions as a trigger of massive star formation
• Massive star formation in the Carina nebula complex and Gum 31 -- I. The Carina nebula complex
• Unraveling the observational signatures of cloud-cloud collision and hub-filament systems in W31
• Detailed CO ($J$ = 1--0, 2--1 and 3--2) observations toward an H{\sc ii} region RCW~32 in the Vela Molecular Ridge
• Unveiling molecular clouds toward bipolar HII region G8.14+0.23
• The study of a system of H II regions toward l = 24.8 deg, b = 0.1 deg at the Galactic bar - Norma arm interface
• AFGL 5180 and AFGL 6366S: sites of hub-filament systems at the opposite edges of a filamentary cloud
• G133.50+9.01: A likely cloud-cloud collision complex triggering the formation of filaments, cores and a stellar cluster
• FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN): Possible evidence of cloud-cloud collisions triggering high-mass star formation in the giant molecular cloud M16 (Eagle Nebula)
• Cloud-cloud collision and star formation in G013.313+0.193
• A Multiwavelength Study of the Sgr B Region: Contiguous Cloud-Cloud Collisions Triggering Widespread Star Formation Events?
• [CII] emission properties of the massive star-forming region RCW36 in a filamentary molecular cloud
• Triggered high-mass star formation in the HII region W28A2: A cloud-cloud collision scenario
• First Search for Low-Frequency CH with a Square Kilometre Array Precursor Telescope
• Massive star formation in the Carina nebula complex and Gum 31 -- II. a cloud-cloud collision in Gum 31