Formation of a massive protostar through disk accretion -: II.: SINFONI integral field spectroscopy of the M 17 silhouette disk and discovery of the associated H2 jet

Context. Recent observational results suggest that high-mass (proto-)stars form in a similar way to low- and intermediate-mass stars, i.e., via disk accretion of gas and dust. Aims. To further characterize and understand the on-going physical processes associated with a large circumstellar disk, seen as a dark silhouette against the bright background of the M17 HII region, we report and discuss new high angular resolution integral field spectroscopy performed in the K-band. Methods. The data were taken with the Adaptive Optics (AO) supported near-infrared integral field spectrograph SINFONI at ESO's Very Large Telescope Yepun (VLT UT 4) as part of the science verification of this new instrument. Results. Based on obtained H-2 v = 1-0 S (1) and H-2 v = 1-0 S (3) emission maps, we report the discovery of a H-2 jet, which apparently arises from the suspected protostellar source(s) located at the very center of the disk. In addition, both diameter (about 4000 AU) and sub-structures of the innermost, densest part of the flared disk are infered from Br gamma, Br delta, and HeI maps. Conclusions. Because ejection of material through a jet/outflow is always linked to accretion of gas and dust either onto the circumstellar disk or onto the central (protostellar) source(s), the presence of a collimated H-2 jet provides indirect but unquestionable evidence for ongoing accretion processes in the case of the M17 disk. The high mass outflow and accretion rates of > 10(-5) M-circle dot yr(-1) derived from the SINFONI data suggest that a star of rather high mass is forming.