College of Science and Health Theses and Dissertations

Date of Award

Summer 8-17-2012

Degree Type


Degree Name

Master of Science (MS)



First Advisor

Anuj Sarma, Ph.D.

Second Advisor

Jesus Pando, Ph.D.

Third Advisor

Gabriela Gonzalez Aviles, Ph.D.


In this thesis we present high angular resolution data on 36 GHz Class I methanol masers associated with sites of 6.7 GHz Class II methanol masers. We observed twenty-three 36 GHz Class I methanol masers in seven star forming regions with the Jansky Very Large Array radio telescope. Our observations have made possible the first high angular resolution maps of 36 GHz masers in several star forming regions, and demonstrated cases where the morphology is highly suggestive of arcs and other structures known to be found at shock interfaces in such regions. The two classes of methanol masers are created through different excitation processes, and occur in different parts of star forming regions. We find that strong 6.7 GHz Class II maser sites are likely associated with weak 36 GHz Class I masers, in agreement with a similar anti-correlation between 44 GHz Class I and 6.7 GHz Class II methanol masers in the literature. However, there is a correlation between 95 GHz Class I and 6.7 GHz Class II masers in the literature. This points to the need for a larger set of high angular resolution data and improved theoretical models of methanol maser pumping and propagation. We find that the center velocities (vLSR) of the observed 36 GHz masers are quite close to the vLSR of 6.7 GHz masers, and in some cases may be closer to the systemic velocity of the region than the vLSR of the 6.7 GHz masers. This could be due to such 36 GHz masers being located at the base of outflows close to the location of the protostar. Finally, comparison of spectral profiles indicates that the strongest 36 GHz masers may lie closer to the 6.7 GHz masers. In summary, such high angular resolution observations that allow for the comparison of the two classes of methanol masers provide a powerful tool to study star forming regions.

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