Dynamical mass modeling of dispersion-supported dwarf galaxies.

摘要

The currently favored cold dark matter cosmology (LCDM) has had much success in reproducing the large scale structure of the universe. However, on smaller scales there are some possible discrepancies when attempting to match galactic observations with properties of halos in dissipationless LCDM simulations. One advantageous method to test small scale simulations with observations is through dynamical mass modeling of nearby dwarf spheroidal galaxies (dSphs).;The stellar tracers of dSphs are dispersion-supported, which poses a significant challenge in accurately deriving mass profiles. Unlike rotationally-supported galaxies, the dynamics of which can be well-approximated by one-dimensional physics, modeling dispersion-supported systems given only line-of-sight data results in a well-known degeneracy between the mass profile and the velocity dispersion anisotropy.;The core of this dissertation is rooted in a new advancement which we have discovered: the range of solutions allowed by the mass-anisotropy degeneracy varies as a function of radius, with a considerable minimal near the deprojected half-light radius of almost all observed dispersion-supported galaxies. This finding allows for a wide range of applications in galaxy formation scenarios to be explored in an attempt to address, amongst other hypotheses, whether the LCDM framework needs to be modified in order to reproduce observations on the small scale.;This thesis is comprised of both the derivation of this finding, and its applicability to all dispersion-supported systems, ranging from dwarfs galaxies consisting of a few hundred stars to systems of 'intracluster light', containing over a trillion stars. Rarely does one have the privilege of working with systems that span such a large range in luminosity (or any intrinsic property) in a short graduate career. Although the large applicability of this scale-free finding allows for discussion in many subfields, this thesis will mainly focus on one topic: dwarf galaxies of the Local Group.