Angular Momentum and the Validity of the Adiabatic Contraction Assumption
Year: 2010
Type: preprint
Abstract: Adiabatic contraction is frequently used to model the effects of baryon condensation on dark matter halos. However, it has recently been shown that this model is not always accurate; authors including Gnedin et al. (2004) and Gustafsson et al. (2006) have found it to be inaccurate at the level of tens of percent. We have analyzed high resolution N-body simulations of dark matter halos, focusing specifically on the evolution of angular momentum, to assess the accuracy of the assumptions of the adiabatic contraction model. We investigate the validity of the assumptions using dark-matter-only halos, in order to provide a limit on how accurate we may expect the adiabatic contraction model to be once baryons are included. In brief, we find that not only is individual particle angular momentum not conserved, but the radial profile and distribution of angular momentum also varies over the age of the Universe by up to factors of a few. We find that torques from external structure are the most likely cause for this distribution shift. This variation implies that there is a fundamental limit on the possible accuracy of the adiabatic contraction model in modeling the response of DM halos to the growth of galaxies.
Source: arXiv (Cornell University)
Institutions: California Institute of Technology, University of Washington
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2267825117