An infrared study of the NGC 7538 region
Infrared observations of the NGC 7538 region at wavelengths from 1 μm to 1 mm are presented and analysed with the aim of understanding both the large-scale structure of this region of current star formation and the properties of the individual compact objects within it. At far-infrared wavelengths (25–130 μm), emission is seen from the visible H II region, from the vicinity of the previously known maser sources and dust-embedded compact H II regions, and from a new region called NGC 7538(E). Coincident with NGC 7538(E) are a point-like 1–25 μm infrared source, NGC 7538-IRS9, which probably provides the power for the far-infrared emission, and an extended source of 2.2 μm emission which appears to be an infrared reflection nebula. NGC 7538-IRS9 strongly resembles the compact H II region NGC 7538-IRS1 in its infrared properties but shows no radio continuum emission. The compact H II regions, the maser sources and IRS9 are located within a dense molecular cloud at the edge of the optical H II region. This cloud, which has M∼9×10³M⊙, is detected in emission at 1 mm. The NGC 7538 region appears to contain examples of different stages in the formation of massive stars; it is suggested that the centre of star formation is moving systematically to the south-east in this region.
Additional Information© 1979 Royal Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1979 February 5; in original form 1978 October 17; Published: 01 October 1979. We thank C. A. Beichman, J. H. Elias, D. A. Harper, J. R. Houck, C. M. Telesco, R. J. van Duinen, the night assistants at the Hale Observatories and Mauna Kea and the staff and crew of the Kuiper Airborne Observatory for their assistant with the observations. We thank G. Forrester for his major contributions to the preparation of the airborne experiment and to the performance of the observations. D. A. Harper, H. A. Thronson and W. J. Wilson kindly made their unpublished data available to us. We thank J. H. Elias and F. P. Israel for helpful discussions and comments on the paper, and J. Boyer, S. Hage and P. Lee for assistance with preparation of the manuscript. This work was supported by NASA Grants NGR 05-002-281 and NGL 05-002-207 and by NSF Grant AST 75-18555A2.
Published - mnras188-0463.pdf