Investigation of the intermediate and high end initial mass function as probed by near-infrared selected stellar clusters

Christine Trombley

Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in October 2013. Physical copy available through RIT's The Wallace Library at: QB853 .T76 2013


Young stellar clusters serve as powerful natural laboratories for studying the intermediate to high mass end of the initial mass function. The purpose of this dissertation is to measure the slope of the stellar initial mass function (IMF) over the intermediate to high mass range. Previous measurements are consistent with a "canonical" value over this mass regime, though the young massive star population in the Galactic Center may have a "top-heavy" distribution. In order to probe the IMF in stellar clusters that are preferentially more distant and more massive than the majority previously studied in the literature, the cluster sample is drawn from catalogs of infrared-selected candidates. Hubble Space Telescope near-infrared imaging is used to select the most promising candidates for young, massive stellar clusters. Follow-up near-infrared spectroscopy from two telescopes, covering the northern and southern latitudes, is used to identify the main sequence population and confirm a young age. The IMF is inferred from mass-magnitude relations using Geneva stellar evolutionary models. The slope at the intermediate to high mass range is measured for the completeness-corrected, background subtracted data. Deviations from the canonical IMF slope are discussed. No strong evidence in support of or against a stellar upper mass limit is found. The slope of the intermediate to high end slope of the IMF, as probed by the near-IR selected stellar clusters in this sample, is determined here to be Gamma=-1.22, to within 0.31 dex, similar to the canonical value of -1.35