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Observations show that radial metallicity gradients in disk galaxies are relatively shallow, if not flat, especially at large galactocentric distances and for galaxies in the high-redshift universe. Given that star formation and metal…
High-resolution imaging of some protoplanetary disks in scattered light reveals presence of the global spiral arms of significant amplitude, likely excited by massive planets or stellar companions. Assuming that these arms are density…
Rings and spiral arms are distinctive features of many galaxies, and their properties are closely related to the disk dynamics. They are often associated to stellar bars, but the details of this connection are far from clear. We study the…
We report the ALMA Cycle 2 observations of the Class I binary protostellar system L1551 NE in the 0.9-mm continuum, C18O (3-2), 13CO (3-2), SO (7_8-6_7), and the CS (7-6) emission. At 0.18" (= 25 AU) resolution, ~4-times higher than that of…
The structure of spiral galaxies is essential to understanding the dynamics and evolution of disk galaxies; however, the precise nature of spiral arms remains uncertain. Two challenges in understanding the mechanisms driving spirals are how…
Large-scale spiral arms have been revealed in scattered light images of a few protoplanetary disks. Theoretical models suggest that such arms may be driven by and co-rotate with giant planets, which has called for remarkable observational…
We propose collisionless damping of fast MHD waves as an important mechanism for the heating and acceleration of winds from rotating stars. Stellar rotation causes magnetic field lines anchored at the surface to form a spiral pattern and…
A method which we have developed for determining corotation radii, has allowed us to map in detail the radial resonant structures of barred spiral galaxies. Here we have combined this information with new determinations of the bar strength…
We seek to understand the origin of radial migration in spiral galaxies by analyzing in detail the structure and evolution of an idealized, isolated galactic disk. To understand the redistribution of stars, we characterize the…
Millimeter continuum spiral arms have so far only been detected in a handful of protoplanetary disks, and thus we have a limited understanding of the circumstances in which they can form. In particular, substructures in small disks…
In an equilibrium axisymmetric galactic disc, the mean galactocentric radial and vertical velocities are expected to be zero everywhere. In recent years, various large spectroscopic surveys have however shown that stars of the Milky Way…
The results of numerical simulations of a gaseous disk in the potential of a stellar spiral density wave are presented. The conditions under which straightened spiral arm segments (rows) form in the gas component are studied. These features…
We model and analyse the secular evolution of stellar bars in spinning dark matter (DM) haloes with the cosmological spin lambda ~ 0 -- 0.09. Using high-resolution stellar and DM numerical simulations, we focus on angular momentum exchange…
Gas response to the underlying stellar spirals is explored for M81 using unmagnetized hydrodynamic simulations. Constrained within the uncertainty of observations, 18 simulations are carried out to study the effects of selfgravity and to…
We investigate the dynamics of magnetic fields in spiral galaxies by performing 3D MHD simulations of galactic discs subject to a spiral potential. Recent hydrodynamic simulations have demonstrated the formation of inter-arm spurs as well…
Star formation is enhanced in spiral arms because of a combination of orbit crowding, cloud collisions, and gravitational instabilities. The characteristic mass for the instability is 10^7 Msun in gas and 10^5 Msun in stars, and the…
In spiral galaxies, the pitch angle, $\alpha$, of the spiral arms is often proposed as a discriminator between theories for the formation of the spiral structure. In Lin-Shu density wave theory, $\alpha$ stays constant in time, being simply…
Stellar orbits in the Galactic disc evolve from their birth to the current shape through both radial migration and dynamical heating. The history of their secular evolution is imprinted in the current kinematics and age-metallicity…
Vertically extended, high velocity dispersion stellar distributions appear to be a ubiquitous feature of disc galaxies, and both internal and external mechanisms have been proposed to be the major driver of their formation. However, it is…
Combining 3D smoothed-particle hydrodynamics and Monte Carlo radiative transfer calculations, we examine the morphology of spiral density waves induced by gravitational instability (GI) in protoplanetary disks, as they would appear in…