High Resolution LAsMA $^{12}$CO and $^{13}$CO Observation of the G305
  Giant Molecular Cloud Complex : I. Feedback on the Molecular Gas
  We observed the G305 star forming complex in the $J=3\text{-}2$ lines of
$^{12}$CO and $^{13}$CO to investigate how molecular gas surrounding the
central stellar clusters is being impacted by feedback. The APEX telescope's
LAsMA multi-beam receiver was used to observe the region. Excitation
temperatures and column density maps were produced. Combining our data with
data from the SEDIGISM survey resulted in a $^{13}$CO $J=3\text{-}2/2\text{-}1$
excitation map. To verify whether feedback from stellar clusters is responsible
for exciting the gas, the distribution of CO excitation was compared with that
of 8$\,\mu\rm{m}$ emission imaged with Spitzer, which is dominated by
UV-excited emission from PAHs. Line centroid velocities, as well as stacked
line profiles were examined to investigate the effect of feedback on the gas
dynamics. Line profiles along radially outward directions demonstrate that the
excitation temperature and $^{13}$CO $J=3\text{-}2/2\text{-}1$ ratio increase
steeply by factors of $\sim\,2-3$ at the edge of the denser gas traced by
$^{13}$CO that faces the hot stars at the center of the complex and steadily
decreases away from it. Column density also increases at the leading edge, but
does not always decrease steadily outward. Regions with higher 8$\,\mu\rm{m}$
flux have higher median excitation temperatures, column densities and $^{13}$CO
$J=3\text{-}2/2\text{-}1$ ratio. The centroid velocity probability distribution
function of the region shows exponential wings, indicative of turbulence driven
by strong stellar winds. Stacked spectra in regions with stronger feedback have
higher skewness and narrower peaks with pronounced wings compared to regions
with weaker feedback. Feedback from the stellar cluster in G305 has
demonstrable effects on the excitation as well as on the dynamics of the giant
molecular cloud.
