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Ring and Lens Formation

Françoise Combes
1996 International Astronomical Union Colloquium  
AbstractThe dynamical mechanism to form rings at Lindblad resonances in a barred galaxy is now well-known: due to its dissipative character, the gas is forced in a spiral structure, and experiences torques  ...  We propose here that lenses are the result of partial bar destruction, a necessary step in a feedback cycle of bar formation-destruction, a cycle driven by gas accretion.  ...  Current views of the ISM are therefore based on self-similar structures, a hierarchy of clouds over several orders of magnitude in scale (Falgarone et Combes al. 1992; Pfenniger k Combes 1994) .  ... 
doi:10.1017/s0252921100049927 fatcat:4fvwv2mhzzegjh6td7er7lsac4

Gaseous flows in galaxies

Francoise Combes
2007 Proceedings of the International Astronomical Union  
The gas component plays a major role in the dynamics of spiral galaxies, because of its dissipative character, and its ability to exchange angular momentum with stars in the disk.  ...  The various time-scales of these gaseous flows are described.  ...  Combes . The data points are from the HI kinematics (Laine et al. 1998a ), and the model circular velocity has been fitted to them.  ... 
doi:10.1017/s1743921308017535 fatcat:sdhuesfxe5divle5xm4jcx24ay

A dynamo model for the magnetic field of the weakly barred galaxy IC 4214

D. Moss, P. Rautiainen, H. Salo
1999 Monthly notices of the Royal Astronomical Society  
A B S T R A C T IC 4214 is a weakly barred galaxy, the observed velocity field of which has been well modelled by a dynamical simulation.  ...  We take the velocity field from this simulation as being representative of that to be found in a class of barred spiral galaxies, and use it as input into a galactic dynamo model.  ...  Their general properties have been modelled by various gas dynamical simulations using analytical or numerical potentials (Schwarz 1981; Combes & Gerin 1985; Byrd et al. 1994) .  ... 
doi:10.1046/j.1365-8711.1999.02191.x fatcat:56drt3zm7rcvdpwqsv5rnerdee

Magnetohydrodynamical non-radiative accretion flows in two dimensions

J. M. Stone, J. E. Pringle
2001 Monthly notices of the Royal Astronomical Society  
The two-dimensional structure of the time-averaged flow is significantly different compared to the hydrodynamical case.  ...  We discuss the limitations imposed on our results by the assumption of axisymmetry and the relatively small radial domain.  ...  RESULTS A Fiducial Model The effect of numerical resolution on the nonlinear stage of the MRI has been examined in a variety of local studies (e.g. HGB).  ... 
doi:10.1046/j.1365-8711.2001.04138.x fatcat:a3w7b3loynhczfjibbgkujhd5a

AGN activity and nuclear starbursts: Sgr A* activity shapes the Central Molecular Zone [article]

Kastytis Zubovas
2015 arXiv   pre-print
In this paper, I use SPH simulations to show that most of these properties can be explained as due to a recent outburst of AGN activity in Sgr A*, the central supermassive black hole of the Milky Way.  ...  The Central Molecular Zone (CMZ) of the Milky Way shows several peculiar properties: a large star formation rate, some of the most massive young star clusters and molecular clouds in the Galaxy, and a  ...  This is a stochastic process, so I turn to numerical simulations to investigate the properties of the structures forming in a perturbed CMZ.  ... 
arXiv:1505.05464v1 fatcat:xzf6dp3manhlfigcjah6jxbh3i

Hydrodynamical simulations of Galactic fountains – I. Evolution of single fountains

C. Melioli, F. Brighenti, A. D'Ercole, E. M. de Gouveia Dal Pino
2008 Monthly notices of the Royal Astronomical Society  
This localized circulation of disk gas does not influence the radial chemical gradients on large scale, as required by the chemical models of the Milky Way which reproduce the metallicity distribution  ...  To this aim, we performed a number of 3D hydrodynamical radiative cooling simulations of the gas in the Milky Way where the whole Galaxy structure, the Galactic differential rotation and the supernovae  ...  E.M.G.D.P. also acknowledges the partial support from grants of the Brazilian Agencies FAPESP and CNPq.  ... 
doi:10.1111/j.1365-2966.2008.13446.x fatcat:rfiwhnci7jdgdb7skgmmokpgwi

Molecular Gas in NUclei of GAlaxies (NUGA)

L. K. Hunt, F. Combes, S. García-Burillo, E. Schinnerer, M. Krips, A. J. Baker, F. Boone, A. Eckart, S. Léon, R. Neri, L. J. Tacconi
2008 Astronomy and Astrophysics  
These are the beginning of two straight dust lanes, which are aligned parallel to an oval distortion, reminiscent of a primary bar, almost perpendicular to the nuclear one.  ...  The CO emission is aligned along the stellar nuclear bar of radius 1 kpc, configured in an elongated structure with two spiral arms at high pitch angle.  ...  This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics  ... 
doi:10.1051/0004-6361:20078874 fatcat:daegzlf5l5h2zgzq2djczdyxnu

Escapees from the bar resonances. Presence of low-eccentricity metal-rich stars at the solar vicinity

S. Khoperskov, P. Di Matteo, M. Haywood, A. Gomez, O. Snaith
2020 Astronomy and Astrophysics  
Understanding radial migration is a crucial point for building relevant chemical and dynamical evolution models of the Milky Way disk.  ...  Once the bar strength reaches its maximum amplitude, some of the stars delivered to the outer disk escape the resonances and some of them settle on nearly circular orbits.  ...  Numerical simulations were carried by using the equipment of the shared research facilities of HPC computing resources at Lomonosov Moscow State University supported by the project RFMEFI62117X0011.  ... 
doi:10.1051/0004-6361/201937188 fatcat:76dgrxskmvdc3ahe5edr5ecmm4

CHEMODYNAMIC EVOLUTION OF DWARF GALAXIES IN TIDAL FIELDS

David Williamson, Hugo Martel, Alessandro B. Romeo
2016 Astrophysical Journal  
We perform a series of smoothed particle hydrodynamics (SPH) simulations of dwarf galaxies in external tidal fields to examine the effects of tides on their metallicities and metallicity gradients.  ...  In our simulated galaxies, gravitational instabilities drive gas inwards and produce centralized star formation and a significant metallicity gradient.  ...  as even lopsided modes can drive gas inwards (Jog & Combes 2009 ).  ... 
doi:10.3847/0004-637x/831/1/1 fatcat:6nhbyqs7kfainl7q3qsrguulfy

A dynamical mechanism for the origin of nuclear rings

Mattia C Sormani, Emanuele Sobacchi, Francesca Fragkoudi, Matthew Ridley, Robin G Treß, Simon C O Glover, Ralf S Klessen
2018 Monthly notices of the Royal Astronomical Society  
However, the fact that gas follows non circular orbits in an external barred potential has profound consequences: it creates a region of reverse shear in which it is energetically favourable to form a  ...  In analogy with the standard theory of accretion discs, our theory is based on shear viscous forces among nested annuli of gas.  ...  So, if everything is forced to remain on a circular orbit, the inner ring must move outwards, and the outer ring moves inwards.  ... 
doi:10.1093/mnras/sty2246 fatcat:lxhmofhfvrbcvkc4igmbjf4na4

Exploring spiral galaxy potentials with hydrodynamical simulations

Adrianne D. Slyz, Thilo Kranz, Hans-Walter Rix
2003 Monthly notices of the Royal Astronomical Society  
where effects like inflows due to numerical viscosity and morphological dependence on gas sound speed are less of a concern than they are in the centers of disks.  ...  In particular, we show that a global least squares analysis is not the optimal method for distinguishing different models as it tends to slightly favor low disk fraction models.  ...  Devriendt for a careful reading of the manuscript and are grateful to the anonymous referee for valuable comments.  ... 
doi:10.1111/j.1365-2966.2003.07166.x fatcat:rkisvh6k3jhbdhlulnyznlwczi

KINEMATIC ANALYSIS OF NUCLEAR SPIRALS: FEEDING THE BLACK HOLE IN NGC 1097

Glenn van de Ven, Kambiz Fathi
2010 Astrophysical Journal  
Next, we use a simple spiral perturbation model to constrain the fraction of the measured non-circular motions that is due to radial inflow.  ...  We present a harmonic expansion of the observed line-of-sight velocity field as a method to recover and investigate spiral structures in the nuclear regions of galaxies.  ...  Moreover, numerical models of dust lanes (e.g., Gerssen & Debattista 2007 ) as well as analytical models of diffuse disks (e.g., Valotto & Giovanelli 2004) show that dust extinction can have a significant  ... 
doi:10.1088/0004-637x/723/1/767 fatcat:jcat2mmuu5ggjgj7uo7t66pcc4

Radial Gas Flows in Colliding Galaxies: Connecting Simulations and Observations

Daisuke Iono, Min S. Yun, J. Christopher Mihos
2004 Astrophysical Journal  
(abridged) We investigate the detailed response of gas to the formation of transient and long-lived dynamical structures induced in the early stages of a disk-disk collision, and identify observational  ...  Non-circular gas kinematics driven by the perturbation of the non-axisymmetric structure can produce distinct emission features in the "forbidden velocity quadrants" of the position-velocity diagram (PVD  ...  The numerical model and the units adopted are briefly summarized in §2.  ... 
doi:10.1086/424797 fatcat:zepmwnljkzc35eatib3gjh2q5i

Escapees from the bar resonances. On the presence of low-eccentricity, metal-rich stars at the Solar vicinity [article]

S. Khoperskov, P. Di Matteo, M. Haywood, A. Gomez, O. N. Snaith
2020 arXiv   pre-print
Understanding radial migration is a crucial point to build relevant chemical and dynamical evolution models of the Milky Way disk.  ...  Once the bar strength reaches its maximal amplitude, some of the stars, delivered to the outer disk, escape the resonances and some of them settle on nearly circular orbits.  ...  ONS acknowledges DIM ACAV+ funding. Article number, page 8 of 9 Khoperskov et al.: Migration of inner disk stars with the bar resonances  ... 
arXiv:1911.12424v2 fatcat:rhvwe3a2nng5vazaouux4fxbdi

Dynamics of galaxies with triaxial haloes

A.A. El-Zant, B. Haßler
1998 New Astronomy  
We study the stability of trajectories near the disk plane of galaxy models with a triaxial dark matter halo component.  ...  It was found that weak discreteness noise can change the fraction of such trajectories significantly and can therefore have important consequences for the modelling of galaxies.  ...  Numerical simulations based on CDM models on the other hand predict no core radius at all, but a density increasing as 1/r in the central areas.  ... 
doi:10.1016/s1384-1076(98)00025-6 fatcat:q5t2t36lnbenfjut2tban4zh3i
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