High-resolution APEX/LAsMA 12CO and 13CO (3-2) observation of
the G333 giant molecular cloud complex : II. Survival and gravitational
collapse of dense gas structures under feedback
We investigate the physical properties of gas structures under feedback in
the G333 complex using data of the 13CO (3-2) line in the LAsMA observation. We
used the Dendrogram algorithm to identify molecular gas structures based on the
integrated intensity map of the 13CO (3-2) emission, and extracted the average
spectra of all structures to investigate their velocity components and gas
kinematics. We derive the column density ratios between different transitions
of the 13CO emission pixel-by-pixel, and find the peak values N(2-1)/N(1-0) ~
0.5, N(3-2)/N(1-0) ~ 0.3, N(3-2)/N(2-1) ~ 0.5. These ratios can also be roughly
predicted by RADEX for an average H2β volume density of ~ 4.2 * 103
cmβ3. A classical virial analysis does not reflect the true physical state
of the identified structures, and we find that external pressure from the
ambient cloud plays an important role in confining the observed gas structures.
For high column density structures, velocity dispersion and density show a
clear correlation, while for low column density structures they do not,
indicating the contribution of gravitational collapse to the velocity
dispersion. For both leaf and branch structures, ΟβNβR always has a
stronger correlation compared to ΟβN and ΟβR. The scaling
relations are stronger, and have steeper slopes when considering only
self-gravitating structures, which are the structures most closely associated
with the Heyer-relation. Although the feedback disrupting the molecular clouds
will break up the original cloud complex, the substructures of the original
complex can be reorganized into new gravitationally governed configurations
around new gravitational centers. This process is accompanied by structural
destruction and generation, and changes in gravitational centers, but
gravitational collapse is always ongoing.Comment: 18 pages, 17 figures, accepted for publication in Astronomy &
Astrophysic