New Insights into the Physical Conditions and Internal Structure of a Candidate Proto-Globular Cluster
Abstract
We present ~0.1" resolution (~10 pc) ALMA observations of a molecular cloud identified in the merging Antennae galaxies with the potential to form a globular cluster, nicknamed the ``Firecracker''. Since star formation has not yet begun at a detectable level in this region, this cloud provides an example of what the birth environment of a globular cluster may have looked like before stars form and disrupt the natal physical conditions. Using emission from 12CO(2-1), 12CO(3-2), 13CO(2-1), HCN(4-3), and HCO+(4-3) molecular lines, we are able to resolve the cloud's structure and find that it has a maximum radius of 28 pc and a mass of (1-9) x 10^6 Msun. We demonstrate that since the cloud appears to be bound (based on its bright, compact morphology), an external pressure in excess of P/k > 10^8 K cm^-3 is required. This is consistent with theoretical expectations that cluster formation requires high pressure environments, much higher than typical values found in the Milky Way. The position-velocity diagram of the cloud and its surrounding material suggests that this high pressure may be produced by ram pressure from the collision of filaments. The relative line strengths of HCN and HCO+ in this region also suggest that these molecular lines can be used as a tracer for the evolutionary stage of a cluster.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23336614F