Related papers: Spiral-arm instability - II: magnetic destabilisat…
Fragmentation of a spiral arm is thought to drive the formation of giant clumps in galaxies. Using linear perturbation analysis for self-gravitating spiral arms, we derive an instability parameter and define the conditions for clump…
Context. Regularly-spaced, star-forming regions along the spiral arms of nearby galaxies provide insight into the early stages and initial conditions of star formation. The regular separation of these star-forming regions suggests spiral…
We study the gravitational instability and fragmentation of primordial protostellar discs by using high-resolution cosmological hydrodynamics simulations. We follow the formation and evolution of spiral arms in protostellar discs, examine…
The origin and types of spiral arms are reviewed with an emphasis on the connections between these arms and star formation. Flocculent spiral arms are most likely the result of transient instabilities in the gas that promote dense cloud…
In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional $N$-body simulations. We confirmed that the…
We investigate dynamical states of grand-design spiral arms in three local galaxies: M51, NGC3627 and NGC628. Based on linear perturbation analysis considering multiple components in the galaxies, we compute instability parameters of the…
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…
Intermediate-scale spurs are common in spiral galaxies, but perhaps most distinctively evident in a recent HST image of M51 (Scoville & Rector 2001). We investigate, using time-dependent numerical MHD simulations, how such spurs could form…
The central theme of this thesis work is to explore the possibilities of spiral arm formations from instabilities formed inside the central region of disc galaxies. These instabilities originate from the central baryonic feedback and have…
Spiral arm structures seen in scattered light observations of protoplanetary disks can potentially serve as signposts of planetary companions. They can also lend unique insights into disk masses, which are critical in setting the mass…
(Abridged) We investigate the growth of spiral-arm substructure in vertically stratified, self-gravitating, galactic gas disks, using local numerical MHD simulations. Our new models extend our previous 2D studies (Kim & Ostriker 2002),…
The majority of astrophysics involves the study of spiral galaxies, and stars and planets within them, but how spiral arms in galaxies form and evolve is still a fundamental problem. Major progress in this field was made primarily in the…
We present the numerical study of the formation of spiral structure in the context of violent relaxation. Initial conditions are the out-of-equilibrium disks of self-gravitating particles in rigid rotation. By that mechanism, robust and…
Context. Observations of polarized radio emission show that large-scale (regular) magnetic fields in spiral galaxies are not axisymmetric, but generally stronger in interarm regions. In some nearby galaxies such as NGC 6946 they are…
Spiral-driven instabilities may drive gas inflow to enhance central star formation in disk galaxies. We investigate this hypothesis using the Sloan Digital Sky Survey (SDSS) in a sample of 2779 nearby unbarred star-forming main-sequence…
One of the scenarios for the formation of grand-design spiral arms in disky galaxies involves their interactions with a satellite or another galaxy. Here we consider another possibility, where the perturbation is instead due to the…
We analyze two-armed global spiral density wave modes generated by gravitational instability in razor-thin, non-viscous, self-gravitating protoplanetary disks to understand the dependence of spiral arm morphology (pitch angle $\alpha$ and…
In this paper we discuss the influence of gravitational instabilities in massive protostellar discs on the dynamics of dust grains. Starting from a Smoothed Particle Hydrodynamics (SPH) simulation, we have computed the evolution of the dust…
We use global MHD galaxy simulations to investigate the effects of spiral arms on the evolution of magnetic fields and star formation within a self-regulated interstellar medium (ISM). The same galaxy is simulated twice: once with…
The causes of spiral structure in galaxies remain uncertain. Leaving aside the grand bisymmetric spirals with their own well-known complications, here we consider the possibility that multi-armed spiral features originate from density…