AR 9952 (Archival Research)

Fri Dec 8 10:34:26 GMT 2023

Principal Investigator: Roeland van der Marel
PI Institution: Space Telescope Science Institute
Investigators (xml)

Title: Stellar Dynamical Models for HST Proper Motion Datasets
Cycle: 12

Dynamical investigations of stellar systems provide crucial information on issues such as central black holes, massive dark halos, and mass segregation. However, when only line-of- sight velocities are available it is often difficult to draw unambiguous conclusions, since models must rely on simplifying assumptions {sphericity, velocity isotropy, etc.}. HST is now causing a revolution in this area, as many projects are underway to measure the internal proper motions of stars in, e.g, globular clusters and the Galactic bulge. However, algorithms and software do not currently exist for adequate dynamical interpretation of these datasets. The current state of the art in dynamical modeling is based on axisymmetric Schwarzschild models, which were pioneered by the PI for studies of black holes in elliptical galaxies. We propose to extend these models by including provisions for dealing with proper motions, mass segregation, and discrete datasets. The observational advances offered by HST can only be properly utilized when theory is advanced simultaneously, and this definitely true for proper motion studies. The proposed project is therefore well-matched to the recently started HST Theory Program. We request one year of funding for a postdoc to support this effort. The software from this project will yield an invaluable tool for the astronomical community for the interpretation of HST proper motion datasets.