| 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, about 1 million years old, and two O-type stars.
Sano et al. present new observations of CO emission line in RCW 36
with Mopra (J=1-0), NANTEN2 (J=2-1), and ASTE (J=3-2). They have
discovered two molecular clouds likely to be physically associated
with the star cluster. The high intensity ratio for CO J = 3–2 / 1–0
found toward both clouds indicates that the gas temperature has been
increased due to heating by the O-type stars. Sano et al. propose
that the O-type stars in RCW 36 were formed by a collision between the
two clouds. with an estimated collision timescale of around 100,000
years. Full details are given in the paper in
Publications of the Astronomical Society of Japan.