Radio observations provide a unique view of black holes in the Universe. This thesis presents low frequency radio images and uses the radio sources in those images to study the evolution of black... Show moreRadio observations provide a unique view of black holes in the Universe. This thesis presents low frequency radio images and uses the radio sources in those images to study the evolution of black holes and galaxies through the age of the Universe. Show less
In this thesis we study the earliest stages of high-mass star formation. Class II methanol masers are only associated with massive star formation and are a unique probe of these environments.... Show moreIn this thesis we study the earliest stages of high-mass star formation. Class II methanol masers are only associated with massive star formation and are a unique probe of these environments. Through observations we have studied where and when the methanol maser emission occur in relation to the protostar. We have found that for a fair fraction of the sources the methanol masers appear on size scales of ca. 1000 AU, in the equatorial region of the massive protostar. It appears that infall, rather than rotation, is the dominant motion. We propose that the maser emission occur close to or in a shock interface, possibly related to the accretion flow of the more extended gas in the protostellar envelope onto an accretion disk. The morphology and kinematics of the thermal methanol gas support the hypothesis that the maser region is also the region where the methanol molecules are released from the icy mantles of the du st grains. We have also estimated the temperature and column density of the methanol gas in the outflows and find evidence for radiative excitation of the methanol gas at the location of the maser emission. Show less
