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Elongated bar-like features are ubiquitous in galaxies, occurring at the centers of approximately two-thirds of spiral disks in the nearby Universe. Due to gravitational interactions between the bar and the other components of galaxies, it…

In this paper I argue that, far from necessarily hindering bar formation in disc galaxies, inner haloes may stimulate it. This constitutes a new instability mechanism by which bars can grow. To show this I use a number of N-body simulations…

Astrophysics · Physics 2007-05-23 E. Athanassoula

The variation of an ionizing flux as a mechanism to stimulate the condensation of a diffuse gas is considered. To illustrate this effect, two situations are examined: one on the context of pregalactic conditions, and the other on the…

Astrophysics · Physics 2007-05-23 Antonio Parravano , Catherine Pech

Longitude-velocity (l-V) diagrams of H I and CO gas in the inner Milky Way have long been known to be inconsistent with circular motion in an axisymmetric potential. Several lines of evidence suggest that the Galaxy is barred, and gas flow…

Astrophysics · Physics 2008-11-26 Benjamin J. Weiner , J. A. Sellwood

We use a Cartesian grid to simulate the flow of gas in a barred Galactic potential and investigate the effects of varying the sound speed in the gas and the resolution of the grid. For all sound speeds and resolutions, streamlines closely…

Astrophysics of Galaxies · Physics 2015-06-23 Mattia C. Sormani , James Binney , John Magorrian

Galactic bars are often suspected to be a channel of gas inflow to the galactic center and trigger central star formation and active galactic nuclei (AGN) activity. However, the current status on this issue based on empirical studies is…

Astrophysics of Galaxies · Physics 2015-06-03 Seulhee Oh , Kyuseok Oh , Sukyoung K. Yi

We have found an effective fueling process to a central region of galaxies with weak bar-like distortion by two dimensional hydrodynamical simulations. Gravitational instability of an elongated gas ring at the inner Lindblad resonance…

Astrophysics · Physics 2015-06-24 Keiichi Wada , Asao Habe

Hydrodynamic simulations suggest that galactic gas disks form when coplanar gas spirals into the inner regions of the disk. We recently presented a simple "modified accretion disk" model of viscous galactic disks in which star-formation is…

Astrophysics of Galaxies · Physics 2023-03-01 Enci Wang , Simon J. Lilly

Many barred galaxies today harbor massive concentrations of gas in their centers, and some are known to possess supermassive black holes (SBHs) and their associated stellar cusps. Previous theoretical work has suggested that a bar in a…

Astrophysics · Physics 2007-05-23 Juntai Shen , J. A. Sellwood

We study the impact of bar-induced non-circular motions on the derivation of galactic rotation curves (RCs) using hydrodynamic simulations and observational data from the PHANGS-ALMA survey. We confirm that non-circular motions induced by a…

Astrophysics of Galaxies · Physics 2025-01-23 Jie Liu , Zhi Li , Juntai Shen

For nearly a century, introduction of nanoparticles to elastomers has yielded extraordinarily tough nanocomposites that are critical to technologies from actuators to tires. The mechanisms by which this reinforcement occurs have…

Soft Condensed Matter · Physics 2025-09-08 Pierre Kawak , Harshad Bhapkar , David S. Simmons

Stars with outflows impinging on ambient gas experience accelerations due to the gravitational feedback from the interaction morphology between the outflow and the ambient gas. Such ``negative dynamical friction'' (NDF), in contrast to the…

Astrophysics of Galaxies · Physics 2024-11-11 Muxin Liu , Lile Wang , Xiaoting Fu , Luis C. Ho

Star-gas interactions can provide gravitational feedback that influences the dynamical evolution of stellar clusters, through processes such as dynamical friction (DF) and its non-dissipative counterpart, negative dynamical friction (NDF).…

Astrophysics of Galaxies · Physics 2026-01-22 Jixuan Yang , Lile Wang , Xinyu Li , Meng Sun , Long Wang , Rainer Spurzem

Cavitation in tubes is a common occurrence in nature and engineering applications. Previous studies of cavitation bubble dynamics mainly consider bubbles in stagnant-water tubes, but the dynamics of cavitation bubbles in tubes with flow is…

Fluid Dynamics · Physics 2024-08-05 Nian Wang , Odumuyiwa A. Odumosu , Tianyou Wang , Zhizhao Che

Condensate banking around wellbores can significantly shorten the production from gas-condensate reservoirs. Different approaches to mitigate this issue have been proposed in the literature, among which gas injection comes out with…

Fluid Dynamics · Physics 2021-10-25 Paula Reis , Marcio Carvalho

Self-consistent hybrid N-body and SPH simulations are used to give a new and coherent interpretation of the main features standing out from the HI and CO longitude-velocity observations within the Galactic bar. In particular, the traces of…

Astrophysics · Physics 2009-10-31 R. Fux

Supplying gas to the galactic central regions is one of key ingredients for AGN activity. I will review various fueling mechanisms for a R ~ 1 kpc region, determined mainly by numerical simulations over the last decade. I will also comment…

Astrophysics · Physics 2007-05-23 Keiichi Wada

Galaxy nuclei are a unique laboratory to study gas flows. High-resolution imaging of the gas flows in galactic nuclei are instrumental in the study of the fueling and the feedback of star formation and nuclear activity in nearby galaxies.…

Astrophysics of Galaxies · Physics 2017-01-11 Santiago Garcia-Burillo

We show that bars in galaxy models having halos of moderate density and a variety of velocity distributions all experience a strong drag from dynamical friction unless the halo has large angular momentum in the same sense as the disk. The…

Astrophysics · Physics 2008-11-26 Victor P. Debattista , J. A. Sellwood

There is now clear evidence, from a variety of studies, that galactic bars contribute to and/or accelerate processes which quench galaxies. However, bars have a variety of strengths and pattern speeds, and previous work has suggested that…

Astrophysics of Galaxies · Physics 2026-04-22 Petra Mengistu , Karen L. Masters , Tobias Geron , R. J. Smethurst , Chris Lintott , B. D. Simmons