%0 Generic
%A Van der Laan, Tessel
%C Heidelberg
%D 2012
%F heidok:13872
%R 10.11588/heidok.00013872
%T Circumnuclear star forming rings in the barred galaxies NGC5248 and NGC6951
%U https://archiv.ub.uni-heidelberg.de/volltextserver/13872/
%X In this thesis I study the gas distribution and dynamics, as well as the stellar populations,  in the circumnuclear star forming rings in the nearby barred galaxies NGC5248  and NGC6951. Circumnuclear star forming rings are regions of high gas and star formation  density in the centers of disk galaxies. These star formation rings can have a  strong influence on the secular evolution of their host galaxies, by halting gas inflow  towards the nucleus. The gas masses that build up in these rings are high and this  consequently leads to intense star formation. This makes circumnuclear star forming  rings also an important tool to build up the stellar (pseudo-)bulge. These two galaxies  were selected because they have very similar global properties (mass, size, metallicity),  but very different circumnuclear regions, both of which containing circumnuclear  star forming rings. Detailed investigation of both, and a comparison between them,  thus provides new detailed insight on the interplay between circumnuclear star forming  rings and the circumnuclear region as a whole.  Three questions are addressed in this work. First of all, I investigate the true effectiveness  of the circumnuclear rings as a gas barrier in both galaxies. I study star  formation progression in these rings and its relation to the gas flow onto the ring. The  age and life span of the circumnuclear rings is derived from the analysis of their stellar  populations. In both galaxies I find that while the circumnuclear rings are effective  barriers, they are not absolute ones. The interplay between the large scale stellar bar,  circumnuclear ring and other dynamical components in the circumnuclear region allows  some gas to flow towards the very center past the ring. I find that the location of  the youngest stars in the ring is close to the inflow position of the gas onto the ring in  both galaxies, consistent with star formation proceeding in a ’pearls-on-a-string’ mechanism  with the youngest ’pearls’ close to the gas inflow location. Finally, I derive ages  of the rings around 1.5 Gyr, which implies that circumnuclear star forming rings have  a significant amount of time to shape the circumnuclear regions of their host galaxies.