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We examined variations in the 160/250 and 250/350 micron surface brightness ratios within 24 nearby (<30 Mpc) face-on spiral galaxies observed with the Herschel Space Observatory to identify the heating mechanisms for dust emitting at these…
The relation of central black hole mass and stellar spheroid velocity dispersion (the M-$\sigma$ relation) is one of the best-known and tightest correlations linking black holes and their host galaxies. There has been much scrutiny…
We study the dynamical evolution of a stellar disk orbiting a massive black hole. We explore the role of two-body relaxation, mass segregation, stellar evolution and binary heating in affecting the disk evolution, and consider the impact of…
The velocity dispersion of stars in the solar neighbourhood thin disc increases with time after star formation. Nordstrom et al. (2004) is the most recent observational attempt to constrain the age-velocity dispersion relation. They fitted…
We investigate the angular momentum evolution of four disk galaxies residing in Milky Way-sized halos formed in cosmological zoom-in simulations with various sub-grid physics and merging histories. We decompose these galaxies kinematically…
We study the vertical stellar distribution of the Milky Way thin disk in detail with particular focus on the outer disk. We treat the galactic disk as a gravitationally coupled, three-component system consisting of stars, atomic hydrogen…
We examine the amplitude of the rotation velocity that can be attributed to the dark matter halos of disk galaxies, focusing on well measured intermediate radii. The data for 60 galaxies spanning a large range of mass and Hubble types,…
The velocity dispersion of cold interstellar gas, sigma, is one of the quantities that most radically affect the onset of gravitational instabilities in galaxy discs, and the quantity that is most drastically approximated in stability…
We examine the relation between stellar mass and central stellar velocity dispersion-the M-sigma relation-for massive quiescent galaxies at z<0.7. We measure the local relation from the Sloan Digital Sky Survey and the intermediate redshift…
Theories of stellar orbit diffusion in disk galaxies predict different rates of increase of the velocity dispersions parallel and perpendicular to the disk plane, and it is therefore of interest to measure the different velocity dispersion…
We present results of numerical N-body simulations of a galactic stellar disk embedded into a spherical dark halo. The non-linear dynamics of bending instabilities developing in the disk is studied. The bending modes, axisymmetric and not,…
The structure of a sample of high-redshift (z=2), rotating galaxies with high star formation rates and turbulent gas velocities of sigma=40-80 km/s is investigated. Fitting the observed disk rotational velocities and radii with a Mo, Mao,…
We analyse the heating of stellar discs by non axisymmetric structures and giant molecular clouds (GMCs) in N-body simulations of growing disc galaxies. The analysis resolves long-standing discrepancies between models and data by…
Dynamical parameters like average velocity dispersion and temperature profile of galaxy clusters are determined using a quasi equilibrium thermodynamic theory. The calculated velocity dispersion results from theory and simulations shows a…
We present the analysis of a suite of simulations run with different particle-and grid-based cosmological hydrodynamical codes and compare them with observational data of the Milky Way. This is the first study to make comparisons of…
Could the velocity spread, increasing with time, in the Galactic disk be explained as a result of gravitational interactions of stars with giant molecular clouds (GMCs) and spiral arms? Do the old open clusters high above the Galactic plane…
Most studies of correlations between X-ray and optical properties of galaxy clusters have used the largest samples of data available, regardless of the morphological types of clusters included. Given the increasing evidence that morphology…
We use a suite of numerical simulations to investigate the mechanisms and effects of radial migration of stars in disk galaxies like the Milky Way (MW). An isolated, collisionless stellar disk with a MW-like scale-height shows only the…
The observed stellar velocity dispersions of galactic discs show that the maximum rotation of a disc is on average 63% of the observed maximum rotation. This criterion can, however, not be applied to small or low surface brightness (LSB)…
Recent theoretical work suggests that it may be common for stars in the disks of spiral galaxies to migrate radially across significant distances in the disk. Such migrations are a result of resonant scattering with spiral arms and move the…