The impact of black holes on the stellar-dynamical properties of early-type galaxies

In this thesis we investigate the impact of supermassive black holes (SMBH) on their host galaxies, and specifically on their stellar kinematics, using two sets of simulations. The first set consists of ten pairs of zoom cosmological simulations, in which each pair uses the same initial conditions but one includes energy feedback from Active Galactic Nuclei (AGN) and the other does not. We then compare the resulting galaxies mocking maps from observational integral field unit (IFU) surveys to investigate the impact of AGN feedback. At high redshift all systems are mostly fast-rotating and disk-like. After z ∼ 1 the AGN simulations result in lower-mass, older, less metal rich and slower-rotating systems, with less disky isophotes in general agreement with observations. Two-dimensional kinematic maps of in-situ and accreted stars show that these differences result from reduced in-situ star formation due to AGN feedback. A full analysis of stellar orbits indicates that galaxies simulated with AGN are typically more triaxial and have higher fractions of x-tubes and box orbits and lower fractions of z-tubes. This trend can also be explained by reduced late in-situ star formation. We introduce a global parameter, ξ3, to characterize the anticorrelation between the third-order kinematic moment h3 and the line-of-sight velocity (V/σ), and compare to ATLAS observations. The kinematic asymmetry parameter ξ3 might be a useful diagnostic for large integral field surveys as it is a kinematic indicator for intrinsic shape and orbital content. We use the same simulations to test two methods for measuring galaxy masses from observations. One is anisotropic Jeans modelling, using two different models for the density profiles: a single power-law and the sum of the deprojected luminosity distribution assuming a stellar mass-to-light ratio plus a power-law for representing dark matter. We successfully recover the mass and density profile of the model galaxy. We compare our real and recovered dark matter fractions with observations from the ATLAS survey, finding that they cover the same range. However the dynamical models are generally not accurate in retrieving the average velocity anisotropy of the system and the density profile slopes. The deviations do not seem to correlate with other model galaxy properties or the presence of AGN feedback. This might be partly related to the modelling trying to capture simulation artifacts caused by insufficient resolution. It indicates that dynamical modelling cannot be reliably applied to current cosmological simulations. The other method is reconstruction of gravitationally lensed sources. We constructed mock lensed images using the simulated galaxies as lenses. Using a source reconstruction code we then recovered the mass of the lens within the Einstein radius to good accuracy and less sensitivity to xviii Zusammenfassung simulation limitations. AGN feedback does not seem to impact the profile slopes of our galaxies. The second set of simulations we analyzed consists of twelve isolated simulations of equaland unequal-mass mergers of elliptical galaxies with stars, dark matter and black holes. The gravitational interactions between black holes and stars during and after the merger are believed to push stars away, leaving a tangentially-biased, cored galaxy. We study this effect in detail by performing a full analysis of the stellar orbits and three-dimensional shape of the merger remnants. The black hole interactions are calculated accurately (to post-Newtonian terms) by employing the KETJU integrator. We find that our remnants are prolate and dominated by x-tube orbits, but with increasing black hole mass the central region becomes more spherical and z-tube orbits take the place of x-tubes. We do not observe the expected decrease in the fraction of box orbits. This could mean that our understanding of the orbital structure of cored elliptical galaxies is incomplete. We connect these results with observable features in the projected kinematic maps.