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We have carried out an investigation of the reddest H II regions in the IRAS Point Source Catalog, namely those sources with Y=log(S 25μ /S 12μ ≥1.3, X=log(S 60μ /S 25μ )≥0.8, and S 100μ ≥500 Jy, with the object of determining their stellar content. Of the twenty-four, thirteen are observable at the Very Large Array, and the results of observations of twelve are presented in this paper. The corresponding radio sources, are generally not resolved at 3″ resolution. From this data and other radio data from the literature, as well as estimated distances to the sources, we have calculated the total luminosity of the contained stars from the IRAS data, and plotted this against the total ionization as determined from the radio flux density

Cepheus A remains a unique radio object. It consists of lines of about 13 H II regions, each of which, it was originally suggested, was produced by a B3 star. However, since the lifetime of each H II region was not expected to be greater than about 1000 years, it was difficult to explain how 13 stars could all be in the same stage of evolution inside such a short time interval, let alone why the stars should form in lines. Recently, two highly variable sources have been detected in the region, which can appear and disappear inside a time interval of about 50-80 days. Also, we have recently reanalyzed some of the data which show that in a line of four objects, one is moving at a speed of 300 km s −1 with respect to the others

The results of a radio-continuum survey of embedded H II regions of a number of relatively nearby molecular clouds of moderate size are reported. A number of flat-spectral-index sources were found, for which flux densities were measured at 1.3, 2.8, and 9 cm. The relationship of these sources with their associated molecular clouds is discussed. It is concluded that (1) the star-forming efficiency of these clouds is 2-3 percent, and possibly as high as 5 percent; (2) early-type stars can form in molecular clouds with mass more than 10,000 solar; (3) studies that predict the most massive star that can form in a molecular cloud of a given mass may be underestimating the mass of the cloud because of selection effects; and (4) an energy-balance criterion for collapse of a molecular clouds, similar to the Jeans criterion but using the turbulence kinetic energy of the cloud rather than the thermal energy, may predict where massive stars form. 34 references.

An investigation has been carried out to detect newly formed early type stars by measuring the continuum radio emission from HII regions in R associations. Ten regions have been detected, attributed to stars in the spectral range 09.5V to B0.5V, and corresponds to a space density of 9 x 10/sup -5/ pc/sup -3/. This is about 1800 times greater than the value for the same type of star in the solar neighborhood. Arguments are presented to show that stars of early B spectral type are probably preferentially formed in R associations.

Past determinations of the physical parameters of the Rosette nebula involving radio spectral line observations have generally employed the assumption of Local Thermodynamic Equilibrium (LTE). We present new recombination line and continuum observations made at 6.5 GHz with the 46-m dish at the Algonquin Radio Observatory, and perform a full non-LTE determination of the electron temperature, electron density and turbulent velocity in the H II region. The energetics and dynamics of the Rosette are reconsidered in the light of these new physical parameters.