Star Formation Triggered by the Interaction between the Expanding Bubble and the IRDC Filament in the Nessie Nebula

The Nessie Nebula, an extremely filamentary Infrared Dark Cloud, contains a bright H II region bubble internally ionized by an OB star cluster. The most luminous protostar in the region, AGAL337.916-00.477, is located precisely at the intersection between the expanding Bubble and the IRDC filament. Both NH3 (3,3) masers (observed with the Australia Telescope Compact Array) and SiO 2-1 emission (observed with the Mopra Telescope) show emission peaks exactly coincident with the luminous protostar. The most likely scenario is that the formation of the protostar has been triggered by an interaction between the expanding bubble and the IRDC filament. This interaction suggests a scenario of bubble-filament interactions in which star formation propagates along an IRDC filament. Such a scenario can explain the tear-dropped shape of the Nessie Bubble, and the location of star clusters, compact H II regions, and the luminous protostar along its western edge.