摘要：Context. Ring-like structures in the interstellar medium (ISM) are
commonly associated with high-mass stars. Kinematic studies of large structures in giant
molecular clouds (GMCs) toward these ring-like structures may help us to understand how
massive stars form.
Aims. The origin and properties of the ring-like structure G345.45+1.50 is investigated through observations of the
13CO(3−2) line. The aim of the observations is to determine the kinematics
in the region and to compare physical characteristics estimated from gas emission with
those previously determined using dust continuum emission. This area in the sky is well
suited for studies like this because the ring is located 1\hbox{$\fdg$}5 above the Galactic plane at 1.8 kpc from the Sun, thus
molecular structures are rarely superposed on our line of sight, which minimizes confusion
effects that might hinder identifying of individual molecular condensations.
Methods. The 13CO(3−2) line was mapped toward the whole ring using the Atacama Pathfinder
Experiment (APEX) telescope. The observations cover 17′ × 20′ in the sky with a spatial
resolution of 0.2 pc and an rms of ~1 K at a spectral resolution of 0.1 km s-1.
Results. The ring is found to be expanding with a velocity of
1.0 km s-1,
containing a total mass of 6.9 ×
103M⊙, which agrees well with
that determined using 1.2 mm dust continuum emission. An expansion timescale of
~3 × 106 yr
and a total energy of ~7 ×
1046 erg are estimated. The origin of the ring might have
been a supernova explosion, since a 35.5 cm source, J165920-400424, is located at the center of the ring without an infrared
counterpart. The ring is fragmented, and 104 clumps were identified with diameters of
between 0.3 and 1.6 pc, masses of between 2.3 and 7.5 ×
102M⊙, and densities of between
~102 and
~
104 cm-3. At least 18% of the clumps are forming stars, as is
shown in infrared images. Assuming that the clumps can be modeled as Bonnor-Ebert spheres,
13 clumps are collapsing, and the rest of them are in hydrostatic equilibrium with an
external pressure with a median value of 4 ×
104 K cm-3. In the region, the molecular outflow IRAS 16562-3959
is identified, with a velocity range of 38.4 km s-1, total mass of 13
M⊙, and kinematic energy of
7 × 1045 erg.
Finally, five filamentary structures were found at the edge of the ring with an average
size of 3 pc, a width of 0.6 pc, a mass of 2 ×
102M⊙, and a column density of
6 ×
1021 cm-2.
关键词：ISM: clouds;stars: massive;stars: formation;dust, extinction;ISM: kinematics and dynamics;ISM: molecules
