HLRB Project h0955
The Origin of Galactic Disks
University Observatory Munich
Proposing Institution
University Observatory Munich
Project Manager
Dr. Markus Wetzstein
Scheinerstr. 1
81679 München
Abstract
An important goal of cosmology is to understand how galaxies form.The most popular scenario for structure formation in the universe is based on the inflationary cold dark matter (CDM) theory, according to which cosmic structures arise fromsmall Gaussian density fluctuations composed of non-relativisticcollisionless particles.The dark matter aggregates into larger and larger clumps as gravitational instability amplifies the weak density perturbations produced at early times in the universe.Gas associated with such dark halos cools and condenses within them,eventually forming the galaxies we see today.In spiral galaxies, stars and gas move on circular orbits. The structure of these galaxies is therefore governed by angular momentum. Although the standard picture of galaxy formation is remarably successful in reproducing many global properties of observed galaxies, we are still far from working out all the processes involved. One of the apparent inconsistency concerns the angular momentum for the formation of disk galaxies. Underthe hypothesis of angular momentum conservation the gas retains itsangular momentum and the CDM theory should reproduce the observed sizes of disk galaxies. Unfortunately, in the N-body simulations the angular momentum leaks away. Much of it is trasferred to the dark matter during galaxy mergers. As a result, the resulting disks in simulations are a factor of 10 too small.We focus on the question: Is the gas retained its initial specificangular momentum during the collapse or is it lost during the merger and why? We want performe a high-resolution cosmological simulationsincluding gas, dark matter and stars to study the formation of a disk in a quiessent halo, that did not experience any recent major merger and can be a good candidate to form a realistic disk galaxy.
