Comparing Positions of Molecular Clouds and Masers in the Milky Way

In my project I compare Thomas Rice's dendrogram catalog of molecular gas in the Milky Way with data from the Bar and Spiral Structure Legacy (BeSSeL) Survey. Rice, a member of Harvard University's class of 2012, created this catalog as his senior thesis. He used the dendrogram technique to segment CO in the Milky Way into individual clouds. The dendrogram creates a tree diagram, in which the leaves are peaks in CO intensity. The BeSSeL Survey found parallaxes for methanol maser sources using the Very Large Baseline Array (VLBA). Because these sources are associated with regions of massive star formation in the spiral arms of the galaxy, their locations in the Milky Way yield information about the star forming regions in the spiral arms. They should correspond to peaks in CO, which were identified as clouds in the dendrogram. By matching points between the catalogs based on their locations and by plotting BeSSeL points directly on the dendrogram, I show correspondence between the two data sets. A parallax distance could be assigned to those clouds that have an associated maser, and these parallax distances could change what we know about the molecular clouds. I also show that the dendrogram technique is a viable automated technique for segmenting CO into clouds and assigning masers to those clouds.