Abstract

Our understanding of evolutionary differences between the general population of local early type galaxies (ETGs) and those with high dust content may be improved through a comparison of their stellar kinematics and populations. Sub-structures in the stellar kinematics and/or young stellar population components can indicate merger activity which may be the source of the dust. This thesis investigates the presence of these features in a sample of 16 nearby, dusty ETGs.

Long-slit optical spectra taken along the galaxies’ major axis using the Robert Stobie Spectrograph on the Southern African Large Telescope, have been reduced to spatially binned 1D spectra. The pPXF package has been used to perform full spectral fitting of these 1D spectra with template spectra from the MILES library, using the penalised-pixel method. Spatial kinematic profiles are presented for 15 of the 16 target galaxies and spatial stellar population profiles for four of the 16. Mass weighted age and metallicity results have been obtained from the central region of 15 of the 16 and show that all contain intermediate to old stellar populations, with mass weighted average population ages greater than ~4×109 yr. A plot of maximum rotational velocity/velocity dispersion versus ellipticity confirmed that these galaxies are mostly rotationally supported and a plot of stellar mass versus metallicity shows increasing metallicity with increasing mass. Ten of the dusty ETGs analysed gave similar kinematic and stellar populations results to the general population of nearby ETGs analysed in the SAURON and ATLAS3D surveys.

Five targets show possible sub-structures in their stellar kinematics, and four have a young stellar population component. While these young stellar population components point to a possible merger origin for some of the dust in those targets, there is no evidence that mergers contributed to the high dust content in all targets in this sample of dusty ETGs. Therefore, these results suggest that there may also be internal origins for the dust.