Detection of carbon monoxide within the Magellanic Bridge

Abstract

The Mopra 22-m and SEST 15-m telescopes have been used to detect and partially map a region of 12CO(1-0) line emission within the Magellanic Bridge, a region lying between the Large and Small Magellanic Clouds (LMC and SMC, respectively). The emission appears to be embedded in a cloud of neutral hydrogen, and is in the vicinity of an IRAS source. The CO emission region is found to have a 60 μm/100 μm flux density ratio typical for 12CO(1-0) detections within the SMC, although it has a significantly lower 12CO brightness and velocity width. These suggest that the observed region is of a low metallicity, supporting earlier findings that the Magellanic Bridge is not as evolved as the SMC and Magellanic Stream, which are themselves of a lower metallicity than the Galaxy. Our observations, along with empirical models based on SMC observations, indicate that the radius of the detected CO region has an upper limit of ∼16 pc. This detection is, to our knowledge, the first detection of CO emission from the Magellanic Bridge and is the only direct evidence of star formation through molecular cloud collapse in this region.