2017ApJ...851..140D

We investigate the star formation processes operating in a mid-infrared bubble N49 site that harbors an O-type star in its interior, an ultracompact H II region, and a 6.7 GHz methanol maser at its edges. The ¹³CO line data reveal two velocity components (at velocity peaks ∼88 and ∼95 km s^–1) in the direction of the bubble. An elongated filamentary feature (length >15 pc) is investigated in each molecular cloud component, and the bubble is found at the interface of these two filamentary molecular clouds. The Herschel temperature map traces all these structures in a temperature range of ∼16-24 K. In the velocity space of ¹³CO, the two molecular clouds are separated by ∼7 km s^–1, and are interconnected by a lower-intensity intermediate velocity emission (i.e., a broad bridge feature). A possible complementary molecular pair at [87, 88] km s^–1 and [95, 96] km s^–1 is also observed in the velocity channel maps. These observational signatures are in agreement with the outcomes of simulations of the cloud-cloud collision process. There are also noticeable embedded protostars and Herschel clumps distributed toward the filamentary features including the intersection zone of the two molecular clouds. In the bubble site, different early evolutionary stages of massive star formation are also present. Together, these observational results suggest that in the bubble N49 site, the collision of the filamentary molecular clouds appears to be operated about 0.7 Myr ago, and may have triggered the formation of embedded protostars and massive stars.