3D MHD simulations of magnetic field evolution and radio polarization of barred galaxies

Kulesza-Żydzik, Barbara; Kulpa-Dybeł, K.; Otmianowska-Mazur, K.; Soida, M.; Urbanik, M.

doi:10.1051/0004-6361/201015036

Cited by 9 publications

(10 citation statements)

References 25 publications

(48 reference statements)

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“…For instance, at t = 2.0 Gyr the magnetic spiral is well defined in the interam region, while at t = 5.5 Gyr it is less visible because it connects with magnetic structures apparent in the bar region. The drift of magnetic arms into the interarm area was described in a number of papers e.g., (Kulesza-Żydzik et al 2009(Kulesza-Żydzik et al , 2010, where the authors concluded that this behavior is caused by difference in the angular velocity of magnetic arms and the gaseous spirals. Namely, the magnetic arms do not corotate with gaseous spiral structure, but they follow the general gas motion in the disk, which has a slightly lower angular velocity.…”

Section: Magnetic Field Evolutionmentioning

confidence: 99%

“…Namely, the magnetic arms do not corotate with gaseous spiral structure, but they follow the general gas motion in the disk, which has a slightly lower angular velocity. However, in Kulesza-Żydzik et al (2009Kulesza-Żydzik et al ( , 2010 no dynamo action was included and the drift of magnetic arms into the interam region is not observed during the whole simulation time but only in the short period of calculation.…”

Section: Magnetic Field Evolutionmentioning

confidence: 99%

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Global Simulations of the Magnetic Field Evolution in Barred Galaxies Under the Influence of the Cosmic-Ray-Driven Dynamo

Kulpa-Dybeł

Otmianowska-Mazur

Kulesza-Żydzik

et al. 2011

ApJ

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We present three-dimensional global numerical simulations of the cosmic-ray (CR) driven dynamo in barred galaxies. We study the evolution of the interstellar medium of the barred galaxy in the presence of non-axisymmetric component of the potential, i.e. the bar. The magnetohydrodynamical dynamo is driven by CRs, which are continuously supplied to the disk by supernova (SN) remnants. No magnetic field is present at the beginning of simulations but one-tenth of SN explosions is a source of a small-scale randomly oriented dipolar magnetic field. In all models we assume that 10% of 10 51 erg SN kinetic energy output is converted into CR energy.To compare our results directly with the observed properties of galaxies we construct realistic maps of polarized radio emission. The main result is that the CR-driven dynamo can amplify weak magnetic fields up to a few µG within a few Gyr in barred galaxies. The obtained e-folding time is equal to 300 Myr and the magnetic field reaches equipartition at time t ∼ 4.0 Gyr. Initially, completely random magnetic field evolves into large-scale structures. An even (quadrupoletype) configuration of the magnetic field with respect to the galactic plane can be observed. Additionally, the modeled magnetic field configuration resembles maps of the polarized intensity observed in barred galaxies. Polarization vectors are distributed along the bar and between spiral arms. Moreover, the drift of magnetic arms with respect to the spiral pattern in the gas density distribution is observed during the whole simulation time.

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Section: Magnetic Field Evolutionmentioning

confidence: 99%

Section: Magnetic Field Evolutionmentioning

confidence: 99%

Global Simulations of the Magnetic Field Evolution in Barred Galaxies Under the Influence of the Cosmic-Ray-Driven Dynamo

Kulpa-Dybeł

Otmianowska-Mazur

Kulesza-Żydzik

et al. 2011

ApJ

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“…On the theoretical side, the formation and evolution of bar substructure has been extensively studied using numerical simulations on hydrodynamical models (e.g. Sanders & Huntley 1976;Roberts et al 1979;van Albada & Roberts 1981;Athanassoula 1992b;Piner et al 1995;Englmaier & Gerhard 1997;Patsis & Athanassoula 2000;Maciejewski et al 2002;Maciejewski 2004a,b;Regan & Teuben 2003Ann & Thakur 2005;Lin et al 2008;Thakur et al 2009) and magnetized models (e.g., Kulesza-Żydzik et al 2009Kulesza-Żydzik et al , 2010Kulpa-Dybe let al 2011;. In particular, Athanassoula (1992b) confirmed the early notion of Prendergast (1962) that dust lanes are shocks in the gas flows.…”

Section: Introductionmentioning

confidence: 99%

Gaseous Structures in Barred Galaxies: Effects of the Bar Strength

Kim

2012

ApJ

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Using hydrodynamic simulations, we investigate the physical properties of gaseous substructures in barred galaxies and their relationships with the bar strength. The gaseous medium is assumed to be isothermal and unmagnetized. The bar potential is modeled as a Ferrers prolate with index n. To explore situations with differing bar strength, we vary the bar mass f bar relative to the spheroidal component as well as its aspect ratio R. We derive expressions as functions of f bar and R for the bar strength Q b and the radius r(Q b ) where the maximum bar torque occurs. When applied to observations, these expressions suggest that bars in real galaxies are most likely to have f bar ∼ 0.25-0.50 and n < ∼ 1. Dust lanes approximately follow one of x 1 -orbits and tend to be more straight under a stronger and more elongated bar, but are insensitive to the presence of self-gravity. A nuclear ring of a conventional x 2 type forms only when the bar is not so massive or elongated. The radius of an x 2 -type ring is generally smaller than the inner Lindblad resonance, decreases systematically with increasing Q b , and slightly larger when self-gravity is included. This evidences that the ring position is not determined by the resonance but by the amount of angular momentum loss at dust-lane shocks. Nuclear spirals exist only when the ring is of the x 2 -type and sufficiently large in size. Unlike the other features, nuclear spirals are transient in that they start out as being tightly-wound and weak, and then due to the nonlinear effect unwind and become stronger until turning into shocks, with an unwinding rate higher for larger Q b . The mass inflow rate to the galaxy center is found to be less than 0.01 M yr −1 for models with Q b < ∼ 0.2, while becoming larger than 0.1 M yr −1 when Q b > ∼ 0.2 and self-gravity is included.

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“…There have been a number of numerical studies on magnetic field distributions in barred galaxies. Depending on how magnetic fields are treated, they can be categorized into two groups: (1) those based on mean-field dynamo theories (e.g., Otmianowska-Mazur et al 1997Moss et al 1998Moss et al , 1999Moss et al , 2001Moss et al , 2007 and (2) those using full magnetohydrodynamic (MHD) simulations (Kulesza-Żydzik et al 2009(Kulesza-Żydzik et al , 2010Kulpa-Dybe l et al 2011). Although numerical models from the first group are successful in obtaining synthetic polarization maps and overall field morphologies comparable to observations, they rely on parameterized turbulent terms in the induction equation that are uncertain.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Magnetohydrodynamic Simulations of Barred Galaxies

Kim

Stone

2012

ApJ

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Barred galaxies are known to possess magnetic fields that may affect the properties of bar substructures such as dust lanes and nuclear rings. We use two-dimensional high-resolution magnetohydrodynamic (MHD) simulations to investigate the effects of magnetic fields on the formation and evolution of such substructures as well as on the mass inflow rates to the galaxy center. The gaseous medium is assumed to be infinitesimally-thin, isothermal, non-self-gravitating, and threaded by initially uniform, azimuthal magnetic fields. We find that there exists an outermost x 1 -orbit relative to which gaseous responses to an imposed stellar bar potential are completely different between inside and outside. Inside this orbit, gas is shocked into dust lanes and infalls to form a nuclear ring. Magnetic fields are compressed in dust lanes, reducing their peak density. Magnetic stress removes further angular momentum of the gas at the shocks, temporarily causing the dust lanes to bend into an "L" shape and eventually leading to a smaller and more centrally distributed ring than in unmagnetized models. The mass inflow rates in magnetized models correspondingly become larger, by more than two orders of magnitude when the initial fields have an equipartition value with thermal energy, than in the unmagnetized counterparts. Outside the outermost x 1 -orbit, on the other hand, an MHD dynamo due to the combined action of the bar potential and background shear operates near the corotation and bar-end regions, efficiently amplifying magnetic fields. The amplified fields shape into trailing magnetic arms with strong fields and low density. The base of the magnetic arms has a thin layer in which magnetic fields with opposite polarity reconnect via a tearing-mode instability. This produces numerous magnetic islands with large density which propagate along the arms to turn the outer disk into a highly chaotic state.

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3D MHD simulations of magnetic field evolution and radio polarization of barred galaxies

Cited by 9 publications

References 25 publications

Global Simulations of the Magnetic Field Evolution in Barred Galaxies Under the Influence of the Cosmic-Ray-Driven Dynamo

Global Simulations of the Magnetic Field Evolution in Barred Galaxies Under the Influence of the Cosmic-Ray-Driven Dynamo

Gaseous Structures in Barred Galaxies: Effects of the Bar Strength

Two-Dimensional Magnetohydrodynamic Simulations of Barred Galaxies

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