High Mass Class I Sources in M 17

Abstract.

The evolutionary stage of newly discovered MIR sources within M 17 has been investigated by 2.2, 10 and 20 μm imaging. Combining our N and Q data with NIR observations for 23 objects we obtain spectral energy distributions that qualify all sources to be of Class I. The observed luminosities range between 35 and 2300 L$_\odot$ indicating that the objects represent the youngest generation of massive early type stars in M 17 still surrounded by relics of their protostellar clouds. The morphology of the 10 and 20 μm emission reveals flattened structures in some cases suggesting for the first time the presence of circumstellar disks around massive stars.