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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…

Astrophysics of Galaxies · Physics 2015-05-27 Bruce G. Elmegreen

Making use of a set of detailed potential models for normal spiral galaxies, we analyze the disk stellar orbital dynamics as the structural and dynamical parameters of the spiral arms (mass, pattern speed and pitch angle) are gradually…

Astrophysics of Galaxies · Physics 2017-02-15 Angeles Pérez-Villegas , Bárbara Pichardo , Edmundo Moreno

Spiral galaxies are common in the local Universe, but their formation, evolution, and interplay with bars remain poorly understood. We use a sample of 391 nearby galaxies from the S$^4$G survey to characterise the winding angle and…

Astrophysics of Galaxies · Physics 2019-10-30 Simón Díaz-García , Heikki Salo , Johan H. Knapen , Martín Herrera-Endoqui

More than a dozen young stars host spiral arms in their surrounding protoplanetary disks. The excitation mechanisms of such arms are under debate. The two leading hypotheses -- companion-disk interaction and gravitational instability (GI)…

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…

Astrophysics of Galaxies · Physics 2017-12-27 Shigeki Inoue , Naoki Yoshida

Spiral galaxies are ubiquitous in the local Universe. However the properties of spiral arms in them are still not well studied, and there is even less information concerning spiral structure in distant galaxies. We aim to measure the most…

Astrophysics of Galaxies · Physics 2025-03-12 Ilia V. Chugunov , Alexander A. Marchuk , Aleksandr V. Mosenkov

Different spiral generation mechanisms are expected to produce different morphological and kinematic features. In this first paper in a series we carefully study the parameters of spiral structure in 155 face-on spiral galaxies, selected…

Astrophysics of Galaxies · Physics 2020-02-05 Sergey Savchenko , Alexander Marchuk , Aleksandr Mosenkov , Konstantin Grishunin

Theoretical studies on the response of interstellar gas to a gravitational potential disc with a quasi-stationary spiral arm pattern suggest that the gas experiences a sudden compression due to standing shock waves at spiral arms. This…

Astrophysics of Galaxies · Physics 2016-12-14 Fumi Egusa , Erin Mentuch Cooper , Jin Koda , Junichi Baba

Galactic magnetic arms have been observed between the gaseous arms of some spiral galaxies; their origin remains unclear. We suggest that magnetic spiral arms can be naturally generated in the interarm regions because the galactic fountain…

Astrophysics of Galaxies · Physics 2015-06-22 Luke Chamandy , Anvar Shukurov , Kandaswamy Subramanian

In this study, we investigated the radial variation of the azimuthal propagation of star formation across the spiral arms in the nearby galaxy NGC 5194 (M51a) by analysing the spatial separation between young star clusters and their nearest…

Astrophysics of Galaxies · Physics 2025-04-14 F. K. Sakhibov , V. S. Kostiuk , A. S. Gusev , E. V. Shimanovskaya

The solar neighborhood contains disc stars that have recently crossed spiral arms in the Galaxy. We propose that boundaries in local velocity distributions separate stars that have recently crossed or been perturbed by a particular arm from…

We study numerically large-scale magnetic field evolution and its enhancement in gaseous disks of spiral galaxies. We consider a set of models with the various spiral pattern parameters and the initial magnetic field strength with taking…

Astrophysics of Galaxies · Physics 2018-01-31 S. A. Khoperskov , S. S. Khrapov

A complete map of the 3D distribution of molecular (CO) gas was constructed using a realistic dynamical model of the gas flow in the barred potential of the Milky Way. The map shows two prominent spiral arms starting at the bar ends…

Astrophysics · Physics 2008-12-19 Peter Englmaier , Martin Pohl , Nicolai Bissantz

We use an N-body simulation to study the 3-D density distribution of spirals, and the resulting stellar vertical velocities. Relative to the disc's rotation, the phase of the spiral's peak density away from the mid-plane trails that at the…

Astrophysics of Galaxies · Physics 2015-06-19 Victor P. Debattista

In this paper, we look to analyse the spiral features of grand-design, multiarmed, and flocculent spiral galaxies using deep optical imaging from DESI Legacy Imaging Surveys. We explore the resulting distributions of various characteristics…

Using the RAVE survey, we recently brought to light a gradient in the mean galactocentric radial velocity of stars in the extended solar neighbourhood. This gradient likely originates from non-axisymmetric perturbations of the potential,…

Nuclear spirals are ubiquitous in galaxy centers. They exist not only in strong barred galaxies but also in galaxies without noticeable bars. We use high-resolution hydrodynamic simulations to study the properties of nuclear gas spirals…

Astrophysics of Galaxies · Physics 2017-05-24 Woong-Tae Kim , Bruce G. Elmegreen

There has recently been growing evidence that broad-line regions (BLRs) in active galactic nuclei have regular substructures, such as spiral arms, which are supported by the fact that the radii of BLRs measured by RM observations are…

Astrophysics of Galaxies · Physics 2023-03-01 Pu Du , Jian-Min Wang

One of the key parameters that characterize spiral arms in disk galaxies is a pitch angle that measures the inclination of a spiral arm to the direction of galactic rotation. The pitch angle differs from galaxy to galaxy, which suggests…

Astrophysics of Galaxies · Physics 2015-06-19 Shugo Michikoshi , Eiichiro Kokubo

We start from the author's metric for a rotating and accelerating Universe and we calculate the force acting on a particle in it. This force consists of two parts: one is derived from a potential, and the other describes a Coriolis force…

General Physics · Physics 2012-05-14 Evangelos Chaliasos