TY - JOUR
T1 - Identification of ionizing sources and young stellar objects in m17
AU - Hanson, Margaret Murray
AU - Peter, S.
N1 - Funding Information:
We are grateful to Richard Joyce for his expertise and guidance in the use of the CRSP instrument. We thank John Bally for useful conversations and Roberto Maiolino for helping us obtain a near-infrared solar spectrum. Charles Lada provided a very detailed and thorough referee report which has helped our presentation. We appreciate continued NSF funding, most recently under grant AST 93-14808. M. M. H. acknowledges support through a graduate fellowship from the Boettcher Foundation and a Dean’s grant from the University of Colorado. P. S. C. appreciates support by PPARC grant GR/J58282 for his extended visit to University College London, where some of the work on this paper was done. NSF grants AST 90-16112 and AST 92-18449 provided the funds that built OSIRIS.
Funding Information:
1Visiting Astronomer, Cerro Tololo Inter-American Observatory and Kitt Peak National Observatory, National Optical Astronomy Observatories, operated by the Associated Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.
PY - 1995/7/20
Y1 - 1995/7/20
N2 - 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.
AB - 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.
KW - H ii regions
KW - ISM: Individual (M17)
KW - Infrared: Stars
KW - Stars: Early-type
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U2 - 10.1086/309591
DO - 10.1086/309591
M3 - Article
AN - SCOPUS:11944267172
SN - 0004-637X
VL - 448
SP - L45-L48
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
ER -