SEARCHING FOR SUBSTRUCTURE IN THE STELLAR POPULATIONS OF DWARF AND GIANT GALAXIES

Abstract

In the paradigm of hierarchical galaxy evolution, substructure is expected to form through tidal interactions, accretion events, or mergers of galaxies and proto galaxies. In this thesis I investigate the spatial distribution of Red Giant Branch (RGB) stars within three Andromeda dwarf satellite galaxies (Lacerta I, Cassiopeia III, and Perseus I) and the spatial distribution of globular clusters around two massive elliptical galaxies (M86 and M84) in an effort to identify such substructure. In the process, I characterize the three Andromeda dwarf satellites by estimating their structural and positional parameters (ellipticity, position angle, half-light radius, Sersic index, Right Ascension and Declination of the galaxy centers). I find a chain of over-densities along the west side of Lacerta I and two filaments northwest and southeast of the center of Cassiopeia III that may be coherent substructures. I find no evidence of substructure within the RGB population of Perseus I, possibly due to its relatively isolated environment. Within the globular cluster systems of M86 and M84, I find three features of interest. The peak surface density of the globular cluster system of M86 is offset from the galaxy’s center, which may be at least partly due to the presence of the dwarf elliptical galaxy NGC 4406B. There exists a bridge of globular clusters between the M86 and M84 with a higher surface density than would be expected. Finally a boxy iso-density contour extends along the southeast side of the globular cluster system of M86.