Star formation in the Magellanic Clouds – III. IR observations of giant H II regions

• Published in: Monthly notices of the Royal Astronomical Society 1986-04, Vol.219 (3), p.603-627
• Main Authors: Jones, Terry Jay, Hyland, A. R., Straw, Steven, Harvey, Paul M., Wilking, Bruce A., Joy, Marshal, Gatley, Ian, Thomas, J. A.
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Normal galaxies. Extragalactic objects and systems (by type); Stellar systems. Galactic and extragalactic objects and systems. The universe
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/219.3.603

We present the results of far-infrared and near-infrared mapping of several H II regions in the LMC and SMC. We also present the results of a continuing search for protostars using NIR techniques. The FIR map of N 159 shows strong 100 and 50 μm emission over the entire 2 × 4 arcmin2 area seen in Hα, with two major peaks closely coinciding with the 843 MHz radio map. A second new IR point source showing no evidence of ionizing radiation (protostar) has been found in N 159. Each protostar lies $\sim30$ off-center on the steep gradient of each FIR peak. N 160 A is nearly as luminous as N 159, but is far more compact. All four LMC H II regions studied in the FIR (N 159, N 160 A, N 59 A, N 158) produce more ionizing radiation than expected for their luminosity. This result is most simply explained by a preponderance of early O stars over lower mass stars in comparison with galactic H II regions or a normal IMF, although density and geometric factors can not be ruled out. The LMC H II regions do not have the high surface brightness cores seen in galactic H II regions such as W49, but on the other hand are more compact than very diffuse galactic H II regions such as DR23.