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
European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: firstname.lastname@example.org
2 Astronomisches Institut der Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
3 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
4 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
Accepted: 12 December 2006
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 M 17 H ii 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 H2 –0 S(1) and H2 –0 S(3) emission maps, we report the discovery of a H2 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 γ, Br δ, and He I 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 H2 jet provides indirect but unquestionable evidence for ongoing accretion processes in the case of the M 17 disk. The high mass outflow and accretion rates of >10-5 derived from the SINFONI data suggest that a star of rather high mass is forming.
Key words: stars: early-type / stars: formation / stars: pre-main sequence / stars: individual: M 17 silhouette disk / ISM: individual objects: M 17
© ESO, 2007