We present mid-infrared ( MIR ) observations , made with the TIMMI2 camera on the ESO 3.6 m telescope , toward 14 young massive star-forming regions .
All regions were imaged in the N band , and nine in the Q band , with an angular resolution of \simeq 1 ^ { \prime \prime } .
Typically , the regions exhibit a single or two compact sources ( with sizes in the range 0.008 - 0.18 pc ) plus extended diffuse emission .
The Spitzer –Galactic Legacy Infrared Mid-Plane Survey Extraordinaire images of these regions show much more extended emission than that seen by TIMMI2 , and this is attributed to polycyclic aromatic hydrocarbon ( PAH ) bands .
For the MIR sources associated with radio continuum radiation ( Paper I ) there is a close morphological correspondence between the two emissions , suggesting that the ionized gas ( radio source ) and hot dust ( MIR source ) coexist inside the H ii region .
We found five MIR compact sources which are not associated with radio continuum emission , and are thus prime candidates for hosting young massive protostars .
In particular , objects IRAS 14593 - 5852 II ( only detected at 17.7 µm ) and 17008 - 4040 I are likely to be genuine O-type protostellar objects .
We also present TIMMI2 N -band spectra of 8 sources , all of which are dominated by a prominent silicate absorption feature ( \simeq 9.7 µm ) .
From these data we estimate column densities in the range ( 7 - 17 ) \times 10 ^ { 22 } cm ^ { -2 } , in good agreement with those derived from the 1.2 mm data ( Paper II ) .
Seven sources show bright [ Ne ii ] line emission , as expected from ionized gas regions .
Only IRAS 12383 - 6128 shows detectable PAH emission at 8.6 and 11.3 µm .