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Based on a high quality $N$-body simulation of a double bar galaxy model, we investigate the evolution of the bar properties, including their size, strength and instantaneous pattern speed derived by using three distinct methods: the…
The Lambda-Cold Dark Matter model explains cosmological observations most accurately till date. However, it is still plagued with various shortcomings at galactic scales. Models of dark matter such as superfluid dark matter, Bose-Einstein…
Several authors recently explored the Black-Hole mass (M_BH) vs. stellar velocity dispersion (sigma_*) relationship for Narrow Line Seyfert 1 galaxies (NLS1s). Their results are more or less in agreement and seem to indicate that NLS1s fill…
We study the dark matter halos of galaxies with galaxy-galaxy lensing using the COMBO-17 survey. This survey offers an unprecedented data set for studying lens galaxies at z=0.2-0.7 including redshift information and spectral classification…
We present the velocity dispersion of red giant branch (RGB) stars in M31's halo, derived by modeling the line of sight velocity distribution of over 5000 stars in 50 fields spread throughout M31's stellar halo. The dataset was obtained as…
We discuss a fast cross-Wigner transform based technique for detecting gravitational wave bursts, and estimating the direction of arrival, using a network of (three) non co-located interferometric detectors. The performances of the detector…
We present H-alpha velocity fields of thirteen giant H II regions in four nearby dwarf irregular galaxies, NGC 2366, Holmberg II, IC 2574, and WLM. We classify the velocity features as well as the morphologies of the H II regions. The…
We present the Waves in Nearby Disk galaxies Survey (WiNDS) consisting of 40 nearby low inclination disk galaxies observed through H$\alpha$ high-resolution Fabry Perot interferometry. WiNDS consists of 12 new galaxy observations and 28…
The strength and vertical distribution of atmospheric turbulence is a key factor determining the performance of optical and infrared telescopes, with and without adaptive optics. Yet, this remains challenging to measure. We describe a new…
Radial velocities measured from near-infrared spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that yields near-infrared radial velocity…
We report on the discovery of two potential polar ring galaxies (PRGs) in the WALLABY Pilot Data Release 1 (PDR1). These untargetted detections, cross-matched to NGC 4632 and NGC 6156, are some of the first galaxies where the Hi…
Motivated by the closest major merger, the Antennae Galaxies (NGC4038/4039), we want to improve our genetic algorithm based modeling code Minga (Theis 1999). The aim is to reveal the major interaction and galaxy parameters, e.g. orbital…
This paper examines several methods of tracing galaxies in N-body simulations and their effects on the derived galaxy statistics, especially measurements of velocity bias. Using two simulations with identical initial conditions, one…
Accurate distances are fundamental to interpreting many measured properties of galaxies. Surprisingly, many of the best-studied spiral galaxies in the Local Volume have distance uncertainties that are much larger than can be achieved with…
We have completed a survey of 30 Virgo cluster galaxies in the Halpha emission-line using Fabry-Perot interferometry. The goal of the survey is to obtain a high angular resolution sample of velocity fields of spirals and to study the…
The planetary nebula luminosity function (PNLF) technique for determining distances to galaxies now has been applied to 34 galaxies, including 6 in the Virgo cluster and 3 in the Fornax cluster. Of these, 16 galaxies are late-type or…
In this paper, we study the rotation curves of the Milky Way galaxy (MW) and Andromeda galaxy (M31) by considering their bulge, disk, and halo components. We model the bulge region by the widely accepted de Vaucouleur's law and the disk…
Intermediate-mass stars are often fast rotators, and hence are centrifugally flattened and affected by gravity darkening. To analyse this kind of stars properly, one must turn to 2D models to compute the visible radiative flux and to take…
Parsec-scale multi-wavelength VLBA polarization observations can be used to study the magnetic-field structures of Active Galactic Nuclei (AGN) based on Faraday Rotation (FR) gradients. A number of transverse FR gradients have been found,…
Typically, stars in galaxies have higher velocities than predicted by Newtonian gravity in conjunction with observable galactic matter. To account for the phenomenon, some researchers modified Newtonian gravitation; others introduced dark…