High mass Class I sources in M 17

Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstr. 150/NA 7, 44780 Bochum, Germany ESO European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile

Corresponding author: M. Nielbock, mnielboc@eso.org

Received: 7 May 2001
Accepted: 16 July 2001

Abstract

The region of M 17 has been imaged at 10.5 and 20.0 μm with the groundbased infrared camera MANIAC. In addition to a prominent diffuse emission bar (450 3) extending southeast to northwest at the interface between the Hii region and the southwestern molecular cloud, the mosaic of 133 single frames at each wavelength revealed 22 compact sources. One of these sources is the Kleinmann-Wright-Object and another was previously identified as the ultra-compact Hii region M 17-UC1. Combining the N-band and Q-band data with near infrared data yielded spectral energy distributions that classifies all sources to be of Class I. The observed luminosities were between 55 and 4775 , which suggests that these sources represent the youngest generation of massive early type stars in M 17 and are surrounded by relics of their protostellar clouds. The morphology of the 10.5 and 20.0 μm emission towards some of the sources reveals flattened structures and may be the first evidence of the presence of circumstellar disks around massive stars.