1997A&A...322..307V

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 the Wood & Churchwell (1989ApJ...340..265W) 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.