The evolution of spiral galaxies in clusters

PhD Ceremony: mw. E. Kutdemir, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: The evolution of spiral galaxies in clusters

Promotor(s): prof.dr. R.F. Peletier

Faculty: Mathematics and Natural Sciences

Contact: Elif Kutdemir, tel. 050-363 4098, e-mail: kutdemir@astro.rug.nl

It is well established that spiral galaxies are efficiently transformed into early type galaxies (mainly lenticulars) in denser regions of the universe. 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 a set of parameters which can measure the irregularity of galaxy velocity fields. Their thresholds are based on local, undisturbed galaxies. Using these parameters, we compare cluster members and field galaxies in the distant universe and 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 z ~ 2 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. Using Spitzer Space Telescope data we find the following results: (i) Elliptical galaxies show a tight relation between the 3.6-4.5 μm color and galaxy mass, but the 3.6-4.5 μm color becomes bluer with increasing mass, contrary to all other broadband colors. (ii) The 3.6-4.5