AKARI OBSERVATIONS OF MASSIVE STAR-FORMING REGIONS INDICATIVE OF LARGE-SCALE CLOUD-CLOUD COLLISIONS

We present our AKARI study of massive star forming regions where a large-scale cloud-cloud collision possibly contributes to massive star formation. Our targets are Spitzer bubbles, which consist of two types of bubbles, closed and broken ones; the latter is a candidate of the objects created by cloud-cloud collisions. We performed mid- and far-infrared surface photometry toward Spitzer bubbles to obtain the relationship between the total infrared luminosity, $L_{IR}$, and the bubble radius, R. As a result, we find that $L_{IR}$ is roughly proportional to $R^{\beta}$ where ${\beta}=2.1{\pm}0.4$. Broken bubbles tend to have larger radii than closed bubbles for the same $L_{IR}$.