University of Groningen
Evolution of dwarf galaxies in the Fornax cluster
Venhola, Aku
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Publication date: 2019
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Venhola, A. (2019). Evolution of dwarf galaxies in the Fornax cluster. Rijksuniversiteit Groningen.
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Propositions
accompanying the dissertation
Evolution of dwarf galaxies in the Fornax cluster
1. Deep multi-band surveys observed with instruments with a large field of view provide a valuable resource for studying the dwarf galaxies in nearby galaxy clusters. Due to the abundance of these low mass galaxies, their low surface brightness, typical colors and morphology can be used as discriminators to effectively obtain cluster memberships for them. (Chapters 2,3,4,5)
2. Ultra diffuse galaxies (UDGs) in the Fornax cluster form a continuum in their optical parameters with other low surface brightness dwarf galaxies. Thus, based on our photometric analysis, there is no evidence that UDGs form a distinct group of objects from other dwarfs. (Chapter 2) 3. Many of the largest low surface brightness dwarfs appear to be asymmetric, indicating that their
large sizes might be temporary and are likely induced by tidal interactions. (Chapter 2)
4. The morphology, intrinsic shapes, colors, effective radii and S´ersic indices of the dwarf galaxies in the Fornax cluster are all correlated with cluster-centric distance. These findings indicate that the cluster environment kinematically heats up these dwarfs and suppresses their star formation. (Chapter 4)
5. The surface brightness profiles and colors of the Fornax cluster dwarf galaxies are consistent with a scenario in which the star formation of galaxies with stellar mass M∗ < 108 M are fully
quenched by ram-pressure stripping when they enter the central parts of the cluster for the first time. More massive galaxies will be able to retain some cold gas in their center, and thus star formation may persist there. Theoretical models of the environmental processes taking place in the Fornax cluster are also consistent with that scenario. (Chapter 4)
6. Taking into account projection effects is essential to interpreting galaxy distributions in clusters. (Chapter 4)
7. The faint-end slope of the dwarf galaxy luminosity function in the Fornax cluster is independent of cluster-centric distance. The luminosity function we obtained is similar to the one found in the center of the Virgo cluster by the Next Generation Virgo Survey (NGVS). (Chapter 4) 8. The Max-Tree Objects (MTO) program outperforms the more widely used object identification
algorithm SExtractor (Bertin & Arnouts, 1996) in detecting low surface brightness objects, both by being more complete in the detections and by measuring more accurate sizes and magnitudes for the identified objects. These improvements obtained using MTO can reduce the selection biases in studies relying on automatic detection and parametric selection of galaxies. (Chapter 5)
9. In order to act against global warming, astronomers should be responsible in selecting conference locations that are easily reachable, and also provide a possibility to take part remotely for a reduced price.
10. In order to do science, one needs to have precise definitions. In order to do good science, one needs to have smart definitions.
11. Increasing governmental control of the focus and form of research done in universities leads to imprudent decisions which can cause damage to many branches of science.
Aku Venhola
