Description
The current best cosmological model, the $\Lambda$ Cold Dark Matter model, successfully explains the large scale structures of the universe. However, this model fails to explain some small scale observations. One key example of this discrepancy between theory and observations is the core-cusp problem. Theoretically, we expect steep inner density profiles for dark matter halos, while observations often find flat inner density profiles.
In this project, we use extragalactic stellar streams to constrain the inner and outer slope of the radial density profile as well as other dark matter halo properties. Stellar streams form when the stars in a smaller galaxy tidally strips, due to a stronger gravitational pull from a larger galaxy. This leads to structures of stars orbiting the larger host galaxy. The new extragalactic stream fitting code, X-Stream, enables the exploration of a huge parameter space regarding stream morphology and dark matter features using 2D images of extragalactic streams. We focus our studies on fitting a model to the stream and shells around the dwarf galaxy NGC 300. Dwarf galaxies contain a large fraction of dark matter compared to larger galaxies, making them excellent systems to investigate the dark matter density profile. We model NGC 300's stream and shells as one structure and use it to constrain the progenitor orbit and halo properties of NGC 300. Additionally, we implement the ability to evaluate multiple radial velocity measurements to the code, X-Stream, instead of only using the on sky 2D spatial stream morphology. We first test the method with simulated streams to check the validity, and subsequently use the method on the dwarf galaxy NGC 4449, which has multiple radial velocity measurements along its stream. This opens up for future, tighter stream model constraints of systems in which radial velocities exist.
| Field of study | Astrophysics |
|---|---|
| Supervisor | Sarah Pearson |