We present the results of millimeter and centimeter continuum observations, made with the IRAM 30m telescope and the VLA, toward a sample of 11 luminous IRAS sources classified as high-mass protostellar object candidates. We find 1.2 mm emission for all (but one) regions likely tracing the dust core in which the massive young stellar object is forming, for which we estimate masses ranging from 10 to 140 Msun. For all the sources, but one, we detect centimeter emission associated with the IRAS source, being compact or ultracompact HII region candidates, with early B-type stars as ionizing stars. The 7 mm emission is partially resolved for the four sources observed at this wavelength, with contribution of dust emission at 7 mm ranging from negligible to 44%. By combining our data with infrared surveys we fitted the spectral energy distribution of the sources. Finally, we find a correlation between the degree of disruption of the natal cloud, estimated from the fraction of dust emission associtaed with the centimeter source relative to the total amount of dust in its surroundings, and the size of the centimeter source. From this correlation, we establish an evolutionary sequence which is consistent with the evolutionary stage expected from maser/outflow/dense gas emission and with the infrared excess.
Download