Dynamics and stellar populations of small stellar systems

PhD ceremony: Mr. M. den Brok, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Dynamics and stellar populations of small stellar systems

Promotor(s): prof. R.F. Peletier, prof. E.A. Valentijn

Faculty: Mathematics and Natural Sciences

The formation of dwarf elliptical galaxies (dEs) in clusters is not well understood. Several processes may be responsible for removing the gas from these galaxies and altering their structure. In the first part of this Thesis, I study the stellar populations and structure of dEs in the Coma cluster, using high-spatial resolution imaging data of the HST/ACS Coma Cluster Treasury Survey.

I measure colour gradients in dwarf and giant early-type galaxies. My results show that dwarf galaxies have, contrary to earlier claims, negative colour gradients. The gradients of dwarf and giant galaxies form a continuous relation as a function of magnitude.

Using a customized Bayesian fitting code, I detect and analyze nuclear star clusters in dwarf galaxies. A non-negiglible number of star clusters are resolved, even at the distance of Coma. I find a surprisingly tight relation between the colour and magnitude of nuclear clusters, which can be explained by a simple self-enrichment model in which gas is enriched during the formation of the cluster.

In the second part of the Thesis, I study the dynamics of nearby (Local Group) objects with a new method based on discrete kinematic tracers. First results clearly show the advantages of not binning the kinematic data. Applications of this method include proper modeling of interloper stars and chemical tagging, which in some cases is essential to avoid biased results. The application of our fitting method to the globular cluster M15 confirms the technical feasibility of discrete fitting and provides strong constraints on the dark central mass.