The evolution of spiral galaxies in clusters

Spiral galaxies are transformed into lenticular galaxies in denser regions of the universe. Therefore, galaxy clusters are very good laboratories for investigating galaxy evolution. In this thesis we look at distant clusters (z~0.4), where galaxies are still in the process of being transformed. We focus on gas in galaxies, as its distribution and motions are sensitive to external impacts. By studying the irregularities in the kinematics of the gas, we try to understand the nature of the interaction processes in galaxy clusters.

We define the irregularities with respect to their thresholds based on local, undisturbed galaxies. We then use this information to investigate how cluster members and field galaxies in the distant universe compare with each other. We find remarkably similar irregularity distributions and fractions for them which most probably indicates that field galaxies at intermediate redshifts are still in the process of building their disks via accretion and mergers. We also make a comparison with $zsim2$ galaxies and find that galaxies at intermediate redshifts have more regular gas kinematics.

In the last part of this thesis we study a different topic and introduce a new tool for studying stellar populations in early type galaxies. We find that the 3.6-4.5 micron color is a good metallicity indicator and together with the Mgb index, it provides a plane where age and metallicity can be obtained without degeneracy.

Vrijdag 5 februari 2010, 16.15 uur
Kapteyn Instituut, Rijksuniversiteit Groningen
Faculteit: Wiskunde en Natuurwetenschappen
Academiegebouw, Broerstraat 5, Groningen

Promotor: Prof. dr. R. F. Peletier
Co-promotor: Dr. B. L. Ziegler