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The amount and distribution of dark matter in galaxies defines the formation, evolution and dynamics of these systems. In this thesis we infer the internal mass distributions of 26 E–Sd galaxies using SAURON and CALIFA two-dimensional stellar kinematic maps. We compare two modeling approaches – fitting a solution of the axisymmetric Jeans equations and the commonly applied asymmetric drift correction (ADC). We show that ADC underestimates the enclosed mass by a factor of ∼3-4 once random motion (velocity dispersion) becomes significant com- pared to ordered motion (streaming), that is, when the ratio of ordered-over-random motion is less than about 1.5. Such kinematics indicate that the stellar mass of the galaxy is not confined to the disk plane, as happens in bulges and thick disks of spiral galaxies, as well as in elliptical galaxies. Since this is frequently realized in our sample, as well as in the general galaxy population, a full line-of-sight integration as provided by solutions of the axisymmetric Jeans equation is needed to reliably infer mass distributions in galaxies. We henceforth use the more realistic Jeans models to estimate the dark matter fraction (fDM), by modeling the total (dynamical) mass-to-light ratio and comparing it with the value derived for stars (baryons) from stellar population models. We find several trends of dark matter fraction with global galaxy properties. Ellipticals (E) and late-type spiral (Scd–Sd) galaxies are the most dark matter-dominated objects, while lenticular (S0) and early-type spirals (Sa–Sb) have significantly smaller dark matter fractions. On average, fDM increases both at highest and lowest galaxy (stellar) masses, and is smaller at intermediate masses. Further, it is also anticorrelated with the ratio of ordered-over-random motion, that is dispersion-dominated galaxies show a higher dark matter fraction. Finally, we investigate the maximum circular velocities and qualitative shape of rotation curves as a function of galaxy morphological type along the Hubble sequence. Peaked rotation curves are found in early-type galaxies, while slowly rising rotation curves are typical for late-type spirals. This confirms predictions of recent simulations of galaxy evolution with local photoionization feedback. More generally, our results for dark matter content and dynamics provide empirical constraints on current and future theoretical models of galaxy evolution across a wide range of galaxy morphological types and masses, and thereby will help us to understand the relevant physical processes.
|Supervisor:||Van de Ven, Dr. Glenn|
|Date of thesis defense:||30 April 2014|
|Date Deposited:||09 May 2014 06:41|
|Faculties / Institutes:||The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie|
|Subjects:||520 Astronomy and allied sciences|