Dr. Jiayi Sun (University of Kentucky)

Sajia Shahrin Neha, Pre-Doctoral Researcher (University of Kentucky)

Title:

Hidden Gems: How Nature Builds the Densest Star Clusters

Abstract:

Most stars today form in modest groups, but a small fraction of star formation proceeds in a far more extreme mode, assembling more than10,000 Msun of stars within space of a few parsecs. The resulting young massive star clusters (YMCs) are natural laboratories for understanding the interplay among gravity, turbulence and energetic radiation and the nearest analogs to the conditions under which most stars in the universe were born. We will describe a multiwavelength study of YMCs forming near the centers of two nearby spiral galaxies. 

With millimeter-wave and radio observations taken with the Atacama Large Millimeter Array (ALMA) and the Very Large Array (VLA), we found more than 70 YMC candidates through their thermal dust and free-free emission, more than tripling the sample size compared to previous works. We place each source in an evolutionary sequence from starless cores to dust embedded proto-clusters and to exposed clusters with strong ionizing radiation. With an adapted version of the ergodic argument, we convert source counts into the durations of all evolutionary stages, thereby constraining the cluster assembly and feedback timescale.

Our mass and size estimates also suggest that these YMCs have high volume densities, surface densities and escape velocities, which explain the high star formation efficiency in such extreme environments. Next-generation facilities such as ALMA's Wideband Sensitivity Upgrade and the ngVLA will extend this census across the entire local galaxy population.