On the selection of ultra-compact HII regions from the IRAS Point Source Catalogue: What the 6.7-GHz methanol maser surveys tell us
نویسنده
چکیده
The detection rate of 6.7-GHz methanol masers in IRAS based surveys is discussed within the framework of a model for the distribution and far-infrared characteristics of embedded ionizing stars in the Galaxy. It is shown that the fainter IRAS sources selected with theWood&Churchwell (1989) criteria have a distribution in Galactic latitude that is completely different from what is expected for embedded ionizing stars. It is concluded that a significant fraction of the fainter sources selected with the Wood & Churchwell criteria are most probably not embedded ionizing stars. The model also predicts that a significant fraction of embedded ionizing stars, primarily the less massive ones, are not expected to be exceptionally bright in the far-infrared and are also expected to be located at very small Galactic latitudes.
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