A numerical study of galaxy mass density profiles

Thumbnail Image
Foyle, Kelly Ann Margaret
Astrophysics , Disk galaxies , Numerical simulations
An understanding of the shape and nature of galaxy density profiles remains a major challenge to galaxy structure studies. The physical mechanisms thought to control these profiles include star formation rates and dynamical interactions, but we focus in this thesis on the contribution of dynamical parameters associated with the dark and baryonic matter. We follow the evolution of mass density profiles, and investigate the development of a truncation radius. Using GADGET-2, an N-body/SPH code with a prescription for star formation and feedback, and the SHARCNET computational facilities, we have generated over 200 galaxy models covering a full range of structural parameters. The galaxy models have a minimum of 1.4 million particles and most are evolved over a period of 10 Gyr. We find that the evolution of the galaxy mass density profile is controlled by the ratio of the disk mass fraction, $m_{d}$, to the halo spin parameter, $\lambda$. The strength of the two-component structure in disk profiles and speed at which this structure develops, is directly proportional to $m_{d}/\lambda$. While the development of a two-component profile is coupled to bar formation, not all barred galaxies develop a two-component profile. We also show that the slope of the outer profile is in close agreement with that of the initial profile and remains stable over time, whereas the inner profile slope evolves considerably. This result will greatly improve comparisons of observed with predicted measures of galaxy density profiles. Our galaxy database is the largest of its kind and a valuable resource for many potential galaxy structural studies. We conclude with a list of future investigations based on our study and new database.
External DOI