Structured star formation in the Magellanic inter-cloud region

Abstract

We use a new contiguous imaging survey conducted using the Dark Energy Camera to investigate the distribution and properties of young stellar populations in the Magellanic inter- Cloud region. These young stars are strongly spatially clustered, forming a narrow chain of low-mass associations that trace the densest HI gas in the Magellanic Bridge and extend, in projection, from the SMCto the outer disc of the LMC. The associations in our survey footprint have ages ≲ 30 Myr, masses in the range~100-1200M⊙ and very diffuse structures with halflight radii of up to~100 pc. The two most populous are strongly elliptical and aligned to ≈ 10°, with the axis joining the centres of the LMC and the SMC. These observations strongly suggest that the young inter-Cloud populations formed in situ, likely due to the compression of gas stripped during the most recent close LMC-SMC encounter. The associations lie at distances intermediate between the two Clouds, and we find no evidence for a substantial distance gradient across the imaged area. Finally, we identify a vast shell of young stars surrounding a central association, that is spatially coincident with a low column density bubble in the HI distribution. The properties of this structure are consistent with a scenario where stellar winds and supernova explosions from massive stars in the central cluster swept up the ambient gas into a shell, triggering a new burst of star formation. This is a prime location for studying stellar feedback in a relatively isolated environment.