FORMATION OF DISK GALAXIES IN ΛCDM USING PARTICLE-BASED HYDRODYNAMICS

Open Access
Author:
Zhu, Qirong
Graduate Program:
Astronomy and Astrophysics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 25, 2016
Committee Members:
  • Yuexing Li, Dissertation Advisor
  • Yuexing Li, Committee Chair
  • Peter Mészáros, Committee Member
  • Steinn Sigurðsson, Committee Member
  • Sarah Shandera, Outside Member
  • William N. Brandt, Committee Member
Keywords:
  • galaxy formation
  • disk galaxy
  • SPH
  • particle-based hydrodynamics
Abstract:
Over the past several decades, the current standard model of cosmology (ΛCDM) has been established. Accurate measurements of cosmological parameters provide us a well defined initial condition where we can connect the tiny fluctuations in the early smooth Universe with the rich structures observed at more recent times using direct numerical simulations. Although the nature of dark matter remains elusive, its dynamic evolution can be well studied since gravity is the only force at play. On large scales, hierarchical structures form in the computer simulations which closely resemble the observed galaxy clustering properties. On small scales, how- ever, various tensions arise when numerical calculations are confronted with the observed galaxies. Nearby dwarf galaxies show significant systematic deviations from the computer calculations of ΛCDM. Thin disk geometries and the lack of luminous classical bulge in many nearby galaxies pose additional challenges to ΛCDM cosmology as well. While disk galaxies in the local Universe are ubiqui- tous, forming realistic disk galaxies in hydrodynamic simulations has proven to be a decade-long challenge. In this dissertation, I present my investigation of a Milky Way-sized galaxy formation using two particle-based methods. A particle-based code is naturally suited in cosmological hydrodynamic simulations because it offers an adaptive and flexible description to gas dynamics. Realistic disk galaxies are formed with both SPH and a new Gizmo code, which combines the strengths of traditional SPH and grid-based method.