| Description |
One fundamental question in astronomy remains that of how galaxies form and evolve. Cosmological simulations and large scale surveys of the past two decades have started to test formation mechanism theories. While the combination of these tools have confirmed predictions of the large scale structure of the Universe, they have exposed a number of issues on smaller scales, especially in the low-mass galaxy regime. It is unclear whether these issues are associated with the simulations or observational constraints. Therefore, detailed studies of low-mass stellar systems are of vital importance in understanding this conflict. It is the goal of this dissertation to provide such information from objects known as ultracompact dwarf galaxies (UCDs). UCDs are a class of compact stellar systems intermediate to that of globular clusters and dwarf galaxies. Recent analyses have shown that the dynamical mass appears to be systematically elevated when compared to the stellar population estimates, which can be explained by central black holes (BH) making up 10-15% of the total mass. In my dissertation, I test this hypothesis in two projects searching for central BHs in three UCDs with the Jeans Anisotropic Modeling (JAM) and Schwarzschild dynamical modeling methods. My first project presents the JAM modeling of two Virgo UCDs, VUCD3 and M59cO. Assuming isotropy, I detect central BHs in both objects with masses of 4:4+2:5 -3:0 X 106M. in VUCD3 and 5:8+2:5 - 2:8 x 106M. in M59cO. These BHs make up an astonishing ~13% and ~18% of the total mass for VUCD3 and M59cO, respectively. My second project presents dynamical modeling using both models, mentioned above, of the most massive UCD, M59-UCD3. The best fit models in the JAM and an axisymmetric Schwarzschild model have BHs ranging from 2:5 5:9 106 M., while a triaxial Schwarzschild model prefers a solution with no BH. However, models with a BH in each technique provide a better fit to the central VRMS profile, and thus I estimate the BH mass to be 4:2+2:1 1:7 x 106 M. These BHs, combined with structural information of each UCD, suggest all three objects are the tidally stripped remnants of ~ 109 - 1010M. galaxies. |
