Triggered massive star formation in the vicinity of WR 48a

Abstract

We utilise Midcourse Space Experiment mid-IR imaging and published data to discuss the (massive) star formation region at galactic longitude ∼305 ◦ , apparently associated with the Wolf Rayet WR 48a and the attendant clusters Danks 1 and 2. A spectacular three lobed wind blown bubble surrounds the aforementioned sources, for which we may infer a minimum age of ∼3 Myr from the presence of the WCL star. Near IR data reveals the presence of numerous embedded sources on the periphery of the wind blown bubble. The presence of coincindent H2O, OH and methanol maser emission is suggestive of ongoing massive star formation, which is suppported by the fluxes of the associated IR sources, and the requisite LyC flux required to support the emission from the subset that have associated ucH  regions. Consideration of the integrated radio flux of the complex implies that a minimum of 31 O7V stars must be present, under the assumption of no photon leakage. Given the age and morphology of the complex and in particular the observation that the central exciting clusters have entirely cleared their natal material, we expect this assumption will be violated, and hence that the true population of massive stars is likely to be significantly larger. If confirmed, the G305 complex represents one of the most massive regions of ongoing triggered star formation currently identified in the galaxy.