Formation of massive stars through disk accretion

Rolf Chini, V. H. Hoffmeister, M. Nielbock, G. M. Scheyda, D. Nürnberger, E. D. Feigelson, K. Getman, L. K. Townsley

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


IR imaging, K-band spectroscopy and X-ray data of the stellar cluster in M 17 suggests three categories of massive young objects: I) "Naked" early-type O-stars in the cluster center that exhibit X-ray emission and normal optical/IR-spectra; they do not show signs for any circumstellar material. II) Late O-type stars, that show X-ray emission and H/He absorption lines in their optical/IR-spectra. There is evidence for extended circumstellar material in the form of elongated L-band nebulae, circumstellar MIR emission from regions of about 10.000 AU in diameter and filaments of He I 1.083 μm. III) Massive stars without X-ray emission, K-band spectra with emission lines of H and He and in some cases with CO band head emission. They are heavily enshrouded and also show elongated L-band nebulae, circumstellar MIR emission from regions of about 4.000 AU and ionized He envelopes. Obviously, M 17 harbors several generations of massive stars: Only the oldest "Category I", located in the cluster center, is free of circumstellar material. "Category II" and "III" comprise younger dust-enshrouded objects of a second generation embedded in the interface of the HII region and the adjacent molecular cloud. Due to the presence of flattened dusty disks and perpendicular gaseous outflows, accretion seems to be important for the formation of stars up to type OS. A population of X-ray emitting sources with(Lbol∼104L⊙) shows CO band head absorption; one source was found to have variable CO absorption as known from FU Orionis stars. New data on the 20.000 AU accretion disk in M 17 reveals a collimated H2 2.122 μm jet with three distinct emission knots that emerges from the disk center. The broad Hα and Call emission lines from the bipolar nebula display blue-shifted absorption originating from accretion disk-driven outflows with velocities of ±500km/s.

Original languageEnglish (US)
Pages (from-to)145-150
Number of pages6
JournalProceedings of the International Astronomical Union
Issue numberS227
StatePublished - 2005

All Science Journal Classification (ASJC) codes

  • Medicine (miscellaneous)
  • Astronomy and Astrophysics
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health
  • Space and Planetary Science


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