# Introduction

Prior to post-main-sequence evolution, ionizing radiation is one of the most important mechanisms by which massive stars influence their surrounding environments. For example, ionizing radiation potentially triggers subsequent star-formation. The influences of massive stars are observed in the form of bubble-shaped emission in the 8 $$\mu$$m band of the Spitzer-GLIMPSE survey of the Galactic Plane (Benjamin 2003). Churchwell et al. (2006); Churchwell et al. (2007) observed bubble-shaped 8 $$\mu$$m emission to be common throughout the Galactic plane. Watson et al. (2008); Watson et al. (2009) found 24 $$\mu$$m and 20 cm emission centered within the 8 $$\mu$$m emission. They interpreted the bubbles seen in the GLIMPSE data as caused by hot stars which ionize their surroundings, creating 20 cm free-free emission, and at larger distances excite PAHs, creating 8 $$\mu$$m emission. Deharveng et al. (2010) also interpreted the bubbles as classical HII regions.

Watson et al. (2010) used 2MASS and GLIMPSE photometery and SED-fitting to analyze the young stellar object (YSO) population around 46 bubbles and found about a quarter showed an overabundance of YSOs near the boundary between the ionized interior and molecular exterior. Bubbles wit