The Formation and Impact of Nascent Globular Star Clusters

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

Star formation is one of the most important processes in determining the properties of our Universe. The formation of stars changes galaxies in a variety of ways. For example, the density of massive stars affects how much material in a galaxy is blasted into intergalactic space. The number of massive stars determines the abundance of heavy elements available to form complex molecules, including those that are the basis of life. The mode of star formation that has the strongest impact on its environment takes place in "super star clusters" (SSCs). These super star clusters pack thousands of violent massive stars into small volumes, and these dense regions of massive stars act as bombs in their host galaxies. Over the last few decades we have gained a wealth of knowledge about super star clusters. For example, it is now known that super star clusters were formed in large numbers at early times in the Universe. It is also known that ancient super star clusters (called "globular clusters") are present in great numbers in the Universe today. However, it is not yet known how these clusters form. Nor is it known how their properties depend on the environment they are born in. This project will use new capabilities of the Atacama Large Millimeter/submillimeter Array (ALMA) and NSF's Very Large Array to advance our knowledge. Observations with these facilities will enable the investigation of the environments in which super star cluster are formed. The investigator will expand her education and outreach program, called "Dark Skies, Bright Kids." The investigator will extend the program to rural communities in Southern Virginia. Results from ALMA have provided tantalizing clues about the origin of super star clusters, including the first known example of a molecular precursor for such a cluster. Follow-up observations are underway to constrain the physical conditions in the molecular cloud before stars have formed. Additional ALMA observations of nascent SSCs (after the stars have formed) have revealed an apparent trend in molecular line strengths and ratios with respect to the evolutionary state of the cluster. The main scientific goals of this program to be addressed with this program include the following: (1) Identify additional molecular precursors to SSCs (increasing the sample size from one), (2) Constrain the physical environments required to form super star clusters, (3) Quantify the star formation efficiencies of these extreme star-forming regions, and (4) Codify the relationship between molecular line strengths and ratios and cluster dynamics. These results will provide templates to help interpret molecular line ratios from unresolved sources in the more distant universe. The observations at radio, millimeter, and sub-millimeter wavelengths required to address these issues are already obtained, currently underway, and planned for proposals this year.