Keisuke Hasegawa

Molecular clouds toward the super star cluster NGC 3603; possible evidence for a cloud-cloud collision in triggering the cluster formation

We present new large field observations of molecular clouds with NANTEN2 toward the super star cluster NGC 3603 in the transitions {sup 12}CO(J = 2-1, J = 1-0) and {sup 13}CO(J = 2-1, J = 1-0). We suggest that two molecular clouds at 13 km s{sup –1} and 28 km s{sup –1} are associated with NGC 3603 as evidenced by higher temperatures toward the H II region, as well as morphological correspondence. The mass of the clouds is too small to gravitationally bind them, given their relative motion of ∼20 km s{sup –1}. We suggest that the two clouds collided with each other 1 Myr ago to trigger the formation of the super star cluster. This scenario is able to explain the origin of the highest mass stellar population in the cluster, which is as young as 1 Myr and is segregated within the central sub-pc of the cluster. This is the second super star cluster along with Westerlund 2 where formation may have been triggered by a cloud-cloud collision.

CLOUD–CLOUD COLLISION AS A TRIGGER OF THE HIGH-MASS STAR FORMATION: A MOLECULAR LINE STUDY IN RCW 120

RCW120 is a Galactic HII region having a beautiful ring shape bright in infrared. Our new CO J=1-0 and J=3-2 observations performed with the NANTEN2, Mopra, and ASTE telescopes have revealed that two molecular clouds with a velocity separation of 20km/s are both physically associated with RCW120. The cloud at -8km/s apparently traces the infrared ring, while the other cloud at -28km/s is distributed just outside the opening of the infrared ring, interacting with the HII region as supported by high kinetic temperature of the molecular gas and by the complementary distribution with the ionized gas. A spherically expanding shell driven by the HII region is usually discussed as the origin of the observed ring structure in RCW120. Our observations, however, indicate no evidence of the expanding motion in the velocity space, being inconsistent with the expanding shell model. We here postulate an alternative that, by applying the model introduced by Habe & Ohta (1992), the exciting O star in RCW120 was formed by a collision between the present two clouds at a colliding velocity ~30km/s. In the model, the observed infrared ring can be interpreted as the cavity created in the larger cloud by the collision, whose inner surface is illuminated by the strong UV radiation after the birth of the O star. We discuss that the present cloud-cloud collision scenario explains the observed signatures of RCW120, i.e., its ring morphology, coexistence of the two clouds and their large velocity separation, and absence of the expanding motion.

The TWO MOLECULAR CLOUDS IN RCW 38: EVIDENCE FOR THE FORMATION OF THE YOUNGEST SUPER STAR CLUSTER IN THE MILKY WAY TRIGGERED BY CLOUD–CLOUD COLLISION

We present distributions of two molecular clouds having velocities of 2 km s

Isolating signatures of major cloud-cloud collisions using position-velocity diagrams

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

and 14 km s

The formation of a Spitzer bubble RCW 79 triggered by a cloud–cloud collision

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Formation of the twin galactic starburst regions NGC 6357 and NGC 6334

toward RCW 38, the youngest super star cluster in the Milky Way, in the

A Massive Molecular Outflow in the Dense Dust Core AGAL G337.916-00.477

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DETAILED MOLECULAR OBSERVATIONS TOWARD THE DOUBLE HELIX NEBULA

CO (

Mitochondrial DNA polymorphisms of D-loop and three coding regions (ND2, ND4, ND5) in three Philippine native cattle: Indicus and Taurus maternal lineages

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