Abstract
IN the course of a radio survey of bright emission nebulæ with the 1,500-ft. Sydney cross-aerial, some fourteen nebulæ were studied at a wave-length of 3.5 m. Six were probably observed in emission, seven were undetectable, and one, NGC 6357, was observed in absorption. The observation of NGC 6357 is the first reported case of absorption of radio waves by an emission nebula ; it leads to an estimate of the electron temperature of the nebula based almost entirely on radio data. In this preliminary communication the observation and its consequences are discussed briefly ; a more complete account of the survey will be given elsewhere.
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References
Bok, B. J., Bester, M. J., and Wade, C. M., “A Catalogue of HII Regions in the Milky Way for Longitudes 250°–355°”, Harvard Report (1954).
Haddock, F. T., Mayer, C. H., and Sloanaker, R. M., Nature, 174, 176 (1954).
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MILLS, B., LITTLE, A. & SHERIDAN, K. Absorption of 3.5-m. Radiation in the Optical Emission Nebula, NGC 6357. Nature 177, 178 (1956). https://doi.org/10.1038/177178a0
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DOI: https://doi.org/10.1038/177178a0
