A mid-infrared imaging survey of star forming regions containing methanol and water maser emission

This thesis presents the first mid-infrared imaging surveys of massive star-forming regions. The first of the two surveys presented here is of 21 sites of massive star formation associated with methanol masers. Recent radio observations of young massive stars revealed that methanol masers tend to exist in linear arrangements. It has been argued that these methanol masers exist in, and delineate, edge-on circumstellar disks. In the mid-infrared survey conducted here, three sources were observed that are elongated at the same position angle as their linear methanol maser distributions. It is believed that these elongated mid-infrared objects are indeed circumstellar disks. Furthermore, for the first time direct evidence has been found showing that methanol masers arise inside the mid-infrared-emitting regions of young stellar objects, indicating that they may be pumped by mid-infrared photons.; The second mid-infrared imaging survey presented here is directed towards 21 star formation regions associated with water maser emission. Water masers are generally believed to be associated with shocks in outflow from young massive stars, however new ammonia images have revealed the presence of 'molecular clumps' directly coincident with water maser emission. It is believed that these clumps are extremely young embedded stellar sources. The mid-infrared water maser survey presented here reveals the detection of 5 possible embedded sources associated with water maser emission.; Though it is generally believed that masers are associated with massive stars, radio studies have shown that many sites of maser emission have no UCHII regions. The most popular explanation for this is that the associated stars are too young to have ionized their surroundings. The lack of UCHII regions for stellar sources associated with methanol masers is most likely because they are generally lower mass, non-ionizing stars, rather than because they are young. The detection of embedded sources in the water maser survey indicates that in the case of water masers, stellar youth plays a role. Furthermore, a better coincidence was found between water masers and mid-infrared sources, than between water masers and radio continuum or near-infrared sources.; Combined, these two surveys provide new insight into the roles masers play in the development of massive stars, and provide much needed data concerning the formation of massive stars in general.