Context :

Aims : Most studies of high-mass star formation focus on massive and/or luminous clumps , but the physical properties of their larger scale environment are poorly known .
In this work , we aim at characterising the effects of clustered star formation and feedback of massive stars on the surrounding medium by studying the distribution of warm gas through mid- J ^ { 12 } CO and ^ { 13 } CO observations .

Methods : We present APEX ^ { 12 } CO ( 6–5 ) , ( 7–6 ) , ^ { 13 } CO ( 6–5 ) , ( 8–7 ) and HIFI ^ { 13 } CO ( 10–9 ) maps of the star forming region G327.36–0.6 with a linear size of \sim 3 pc \times~ { } 4 pc .
We infer the physical properties of the emitting gas on large scales through a local thermodynamic equilibrium analysis , while we apply a more sophisticated large velocity gradient approach on selected positions .

Results : Maps of all lines are dominated in intensity by the photon dominated region around the H ii region G327.3–0.5 .
Mid- J ^ { 12 } CO emission is detected over the whole extent of the maps with excitation temperatures ranging from 20 K up to 80 K in the gas around the H ii region , and H _ { 2 } column densities from few 10 ^ { 21 } cm ^ { -2 } in the inter-clump gas to 3 \times 10 ^ { 22 } cm ^ { -2 } towards the hot core G327.3–0.6 .
The warm gas ( traced by ^ { 12 } and ^ { 13 } CO ( 6–5 ) emission ) is only a small percentage ( \sim 10 % ) of the total gas in the infrared dark cloud , while it reaches values up to \sim 35 % of the total gas in the ring surrounding the H ii region .
The ^ { 12 } CO ladders are qualitatively compatible with photon dominated region models for high density gas , but the much weaker than predicted ^ { 13 } CO emission suggests that it comes from a large number of clumps along the line of sight .
All lines are detected in the inter-clump gas when averaged over a large region with an equivalent radius of 50″ ( \sim 0.8 pc ) , implying that the mid- J ^ { 12 } CO and ^ { 13 } CO inter-clump emission is due to high density components with low filling factor .
Finally , the detection of the ^ { 13 } CO ( 10–9 ) line allows to disentangle the effects of gas temperature and gas density on the CO emission , which are degenerate in the APEX observations alone .

Conclusions :