N-body Simulations of the Formation of Exponential Surface Profiles of Galaxy Disks
Abstract
The exponential law of radial surface-brightness profiles in disk galaxies, and some types of dwarf galaxies has long been observed, but recently has been pursued to very low surface brightness levels. Current dynamical theories on accretion of viscous gas, secular disturbances from bars, radial migration due to spiral arms, and interaction with satellite galaxies cast light on the physics behind the formation of an exponential profile. However, none of these theories are capable of completely explaining the ubiquity of exponentials across various galaxy types. N-body simulations with Gadget-2 code provide another way to study exponential profiles. The gravitational attraction of massive clumps, which represent giant clouds or stellar clusters (especially in young disks), scatter stars and alter stellar density profiles from different initial shapes towards exponentials. Scattering increases the stellar velocity dispersion, and the evolution of a radial profile is accompanied by disk thickening. The timescale of the evolution correlates with local gravitational stability of the stellar disk and is sensitive to the masses of individual scattering centers. Low stability and high scattering mass can generate exponential forms quickly. Transient phase mixing and violent relaxation occurring in a disk with a low Toomre Q factor can also accelerate the evolution towards an exponential.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23525003W