ALMA Data Cubes and Continuum Maps of the Irradiated Western Wall in Carina

Abstract

Abstract We present Atacama Large Millimeter/submillimeter Array observations of the continuum and line emission of 12CO, 13CO, C18O, and [C i] for a portion of the G287.38-0.62 (Car 1-E) region in the Carina star-forming complex. The new data record how a molecular cloud responds on subarcsecond scales when subjected to a powerful radiation front, and provide insights into the overall process of star formation within regions that contain the most-massive young stars. The maps show several molecular clouds superpose upon the line of sight, including a portion of the Western Wall, a highly irradiated cloud situated near the young star cluster Trumpler 14. In agreement with theory, there is a clear progression from fluoresced H2, to [C i], to C18O with distance into the photodissociation region (PDR) front. Emission from optically thick 12CO extends across the region, while 13CO, [C i] and especially C18O are more optically thin, and concentrate into clumps and filaments closer to the PDR interface. Within the Western Wall cloud itself we identify 254 distinct core-sized clumps in our data cube of C18O. The mass distribution of these objects is similar to that of the stellar initial mass function. Aside from a large-scale velocity gradient, the clump radial velocities lack any spatial coherence size. There is no direct evidence for triggering of star formation in the Western Wall in that its C18O clumps and continuum cores appear starless, with no pillars present. However, the densest portion of the cloud lies closest to the PDR, and the C18O emission is flattened along the radiation front.