Identification of ionizing sources and young stellar objects in m17

Margaret Murray Hanson, S. Peter

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


We have obtained high-quality 2 (k -band) spectra of 25 stars in the direction of the heavily extincted, Galactic star-forming region M17. Interloping cool field giants are a potential source of confusion, but k-band spectra combined with normal JHK colors can identify and distinguish these stars via their strong CO absorption features at ƛ a 2.29 μm.Amongtheother sources, we have identified fivestarsasO type fromtheirspectral lines of H i, He I, He II, and N iii by using a K-band classification system that we have developed. These provide the number of Lyman-continuum photons required by radio continuum observations. The remaining stellar objects, all but one with strong near-infrared (NIR) excesses, show completely different spectral characteristics from known main-sequence stars. Three are completely featureless throughout the K band, four (possibly five) show CO bands in emission, and two (candidate FU Orionis-like objects) have CO bands in absorption combined with extreme NIR excesses. We suggest that these stellar objects are relatively massive young stellar objects, still shrouded by circumstellar material.

Original languageEnglish (US)
Pages (from-to)L45-L48
JournalAstrophysical Journal
Issue number1
StatePublished - Jul 20 1995


  • H ii regions
  • ISM: Individual (M17)
  • Infrared: Stars
  • Stars: Early-type

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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