Modeling and Observations of Massive Star Cluster Formation

Whelan, David, Astronomy - Graduate School of Arts and Sciences, University of Virginia
Johnson, Kelsey, Department of Astronomy, University of Virginia

In the Universe’s panoply of star forming environments, super star clusters stand out as the most impressive. Their high densities, masses, and gas pressures are the extremes. But because so few examples exist in the Milky Way, and most are observed in distant blue compact dwarf galaxies, merger overlap regions, and similarly turbulent environments, details about their formation and early evolution remain obscure unknowns.

In this dissertation, I outline my modeling efforts that provide useful observables to studies of both embedded and optically visible high mass star forming environments. New dust radiative transfer models provide a set of infrared colors that will help determine some basic envelope properties; their use will only be fully realized with the advent of the James Webb Space Telescope. Likewise, models of the molecular emission from the envelope sheds new light on our understanding of the geometry in these regions, and highlights the ways in which future Atacama Large Millimeter/submillimeter Array observations will shed light on super star cluster formation.

Observations of a superassociation in the SMC provide some intriguing new insights into the dust and molecular properties of giant HII regions at low metallicity and in hard radiation fields. And finally, Hi recombination line models offer compelling evidence that line pumping by the stellar continuum in HII regions, and the subsequent line fluorescence, while important for the interpretation of Hydrogen line fluxes, can easily be overestimated with low-resolution input spectra.

By modeling aspects of massive star cluster evolution from when they are deeply embedded in their natal molecular cloud until they are surrounded by an HII region, I have touched upon some of the most important aspects relating their physical properties with their observable properties. Future observations and models are planned to continue these investigations and provide concrete answers to many of the questions that remain about massive cluster formation.

PHD (Doctor of Philosophy)
astronomy, astrophysics, star formation
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