Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: ALMA CO Observations of a Giant Molecular Cloud in M33: Evidence for
  High-Mass Star Formation Triggered by Cloud-Cloud Collisions   We report the first evidence for high-mass star formation triggered by
collisions of molecular clouds in M33. Using the Atacama Large
Millimeter/submillimeter Array, we spatially resolved filamentary structures of
giant molecular cloud 37 in M33 using $^{12}$CO($J$ = 2-1), $^{13}$CO($J$ =
2-1), and C$^{18}$O($J$ = 2-1) line emission at a spatial resolution of $\sim$2
pc. There are two individual molecular clouds with a systematic velocity
difference of $\sim$6 km s$^{-1}$. Three continuum sources representing up to
$\sim$10 high-mass stars with the spectral types of B0V-O7.5V are embedded
within the densest parts of molecular clouds bright in the C$^{18}$O($J$ = 2-1)
line emission. The two molecular clouds show a complementary spatial
distribution with a spatial displacement of $\sim$6.2 pc, and show a V-shaped
structure in the position-velocity diagram. These observational features traced
by CO and its isotopes are consistent with those in high-mass star-forming
regions created by cloud-cloud collisions in the Galactic and Magellanic Cloud
HII regions. Our new finding in M33 indicates that the cloud-cloud collision is
a promising process to trigger high-mass star formation in the Local Group.

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The categories of this paper are: dg-ga
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin