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Measuring Star Formation Histories of Nuclear Star Clusters to Constrain Formation Methods

Presentation #548.02 in the session “Stellar Evolution and Populations”.

Published onJan 11, 2021
Measuring Star Formation Histories of Nuclear Star Clusters to Constrain Formation Methods

Nuclear star clusters (NSCs) are the densest stellar systems in the universe and are found in roughly 75% of all galactic centers. Currently, there are two dominant theories to explain NSC formation. The cluster in-spiral method involves the migration of massive star clusters that formed outside the nucleus (i.e. globular clusters) into the center of the galaxy. The other method, known as ”In Situ” formation, involves the cluster’s stars forming from gas brought into the nucleus of the galaxy. There is evidence that both methods play a role in NSC formation simultaneously. This research aims to spatially resolve the star formation histories within nearby NSCs to separate out the presence of the different populations formed from these two mechanisms, using long-slit spectroscopic observations with HST’s STIS instrument of three early-type galaxies harboring NSCs (NGC 5102, NGC 5206, and NGC 205). These spectra are measured for each NSC along their major axis. We use the pPXF spectral fitting software to measure the mean age and metallicity at each radius. Using this information along with existing kinematic data for each cluster, constraints will be placed on the formation mechanism responsible for the stellar populations at different locations within each NSC. If the cluster in-spiral formation method is dominant in a stellar population, old/metal-poor stars are expected along with more random motions while ”In Situ” formation would contain a population of young/metal-rich stars with more coherent motions as they likely formed in a gaseous disk. This study will aid in furthering our understanding of where these intrinsically fascinating objects come from.

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