April 21, 2023
2:30 pm (IST)
On the Dynamics of Dwarf Galaxies and Nuclear Objects in a Fuzzy Dark Matter Halo
Dhruba Dutta Chowdhury (Hebrew University)
Abstract: Fuzzy Dark Matter (FDM), consisting of ultralight bosons, is an intriguing alternative to Cold Dark Matter (CDM). Unlike in CDM, FDM halos consist of a central solitonic core, surrounded by an envelope of order unity density fluctuations. The envelope density fluctuations also interact with the soliton causing it to wobble and oscillate. Using novel, high-resolution numerical simulations of an FDM halo corresponding to a particular boson mass, I will demonstrate that the gravitational potential fluctuations associated with the soliton's wobble, its oscillations, and the envelope density fluctuations dynamically heat nuclear objects (e.g., central star clusters and supermassive black holes) and dwarf galaxies. As a result, nuclear objects, initially located at rest at the soliton center, migrate outwards over time until the outward motion is counteracted by dynamical friction and an equilibrium is reached. Similarly, dwarf galaxies continue to increase their sizes and central velocity dispersions. In addition, their kinematic structures become strongly radially anisotropic, especially in the outskirts. Dynamical heating also causes initially ellipsoidal galaxies to become more spherical over time from the inside out and gives rise to distorted, non-concentric isodensity contours. Generalizing these results for other halo and boson masses and comparing them with observations (such as galaxy size-age relation, morphologies, measured offsets of supermassive black holes and nuclear star clusters from the centers of their host galaxies) can potentially constrain the boson mass.