Long-lived transient structure in collisionless self-gravitating systems

Benhaiem, David; Labini, Francesco Sylos; Joyce, Michael

doi:10.1103/physreve.99.022125

Cited by 17 publications

(21 citation statements)

References 63 publications

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“…In order to test the effects of the deviations from a stationary configuration and axisymmetry on the Jeans equation, we consider N-body simulations of mock galactic systems that are not completely in an equilibrium configuration. The evolution of these systems was discussed in details in Benhaiem et al (2017Benhaiem et al ( , 2019Sylos Labini et al (in prep.). We consider, hereafter, one of these systems, consisting of a thin, rotating, selfgravitating disk embedded in an ellipsoidal dark matter halo with an isotropic velocity dispersion.…”

Section: Corrections To the Jeans Equationmentioning

confidence: 99%

Gaia-DR2 extended kinematical maps

Chrobáková

López-Corredoira

Labini

et al. 2020

A&A

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Context. Recent statistical deconvolution methods have produced extended kinematical maps in a range of heliocentric distances that are a factor of two to three larger than those analysed in Gaia Collaboration (2018, A&A, 616, A11) based on the same data. Aims. In this paper, we use such maps to derive the rotation curve both in the Galactic plane and in off-plane regions and to analyse the density distribution. Methods. By assuming stationary equilibrium and axisymmetry, we used the Jeans equation to derive the rotation curve. Then we fit it with density models that include both dark matter and predictions of the MOND (Modified Newtonian dynamics) theory. Since the Milky Way exhibits deviations from axisymmetry and equilibrium, we also considered corrections to the Jeans equation. To compute such corrections, we ran N-body experiments of mock disk galaxies where the departure from equilibrium becomes larger as a function of the distance from the centre. Results. The rotation curve in the outer disk of the Milky Way that is constructed with the Jeans equation exhibits very low dependence on R and z and it is well-fitted both by dark matter halo and MOND models. The application of the Jeans equation for deriving the rotation curve, in the case of the systems that deviate from equilibrium and axisymmetry, introduces systematic errors that grow as a function of the amplitude of the average radial velocity. In the case of the Milky Way, we can observe that the amplitude of the radial velocity reaches ∼10% that of the azimuthal one at R ≈ 20 kpc. Based on this condition, using the rotation curve obtained from the Jeans equation to calculate the mass may overestimate its measurement.

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Section: Corrections To the Jeans Equationmentioning

confidence: 99%

Gaia-DR2 extended kinematical maps

Chrobáková

López-Corredoira

Labini

et al. 2020

A&A

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“…To explore such a dynamical mechanism, Benhaiem et al (2017Benhaiem et al ( , 2019 studied the properties of the systems formed from the pure gravitational evolution of relatively simple initial conditions (IC). Such systems, although extremely simplified, can give interesting insights as to the dynamics of the monolithic collapse.…”

Section: A Violent Origin Of the Galactic Diskmentioning

confidence: 99%

Gaia-DR2 extended kinematical maps

López-Corredoira

Garzón

Wang

et al. 2020

A&A

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Context. In our Paper I, by using statistical deconvolution methods, extended kinematics maps of Gaia-DR2 data have been produced in a range of heliocentric distances that are a factor of two to three larger than those analyzed previously by the Gaia Collaboration with the same data. It added the range of Galactocentric distances between 13 kpc and 20 kpc to the previous maps. Aims. Here, we investigate the dynamical effects produced by different mechanisms that can explain the radial and vertical components of these extended kinematic maps, including a decomposition of bending and breathing of the vertical components. This paper as a whole tries to be a compendium of different dynamical mechanisms whose predictions can be compared to the kinematic maps. Methods. Using analytical methods or simulations, we are able to predict the main dynamical factors and compare them to the predictions of the extended kinematic maps of Gaia-DR2. Results. The gravitational influence of Galactic components that are different from the disk, such as the long bar or bulge, the spiral arms, or a tidal interaction with Sagittarius dwarf galaxy, may explain some features of the velocity maps, especially in the inner parts of the disk. However, they are not sufficient in explaining the most conspicuous gradients in the outer disk. Vertical motions might be dominated by external perturbations or mergers, although a minor component may be due to a warp whose amplitude evolves with time. Here, we show with two different methods, which analyze the dispersion of velocities, that the mass distribution of the disk is flared. Despite these partial explanations, the main observed features can only be explained in terms of out-of-equilibrium models, which are either due to external perturbers or to the fact that the disk has not had time to reach equilibrium since its formation.

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“…This provides an alternative scenario from the standard framework of this issue, which believes that the spiral pattern is the perturbed component of the disk or bulge in equilibrium (Goldreich & Lynden‐Bell 1965; Lin & Shu 1964) or the tidal tails by the passage of a companion object (Toomre & Toomre 1972). The subsequent work of the same group explores further and demonstrates that some specific structures, such as bar and ring, are also obtainable through the same mechanism (Benhaiem et al 2019). In this work, we present the numerical study of the formation of a spiral pattern through the violent relaxation starting from an out‐of‐equilibrium rotating system with rigid rotation.…”

Section: Introductionmentioning

confidence: 95%

Formation of spiral structure from the violent relaxation of self‐gravitating disks

Worrakitpoonpon

2020

Astron Nachr

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We present the numerical study of the formation of a spiral structure in the context of violent relaxation. Initial conditions are the out‐of‐equilibrium disks of self‐gravitating particles in rigid rotation. Using that mechanism, robust and nonstationary spiral arms can be formed within a few free‐fall times through the shearing of mass ejection following the collapse. With a closer look, we find different properties of the arms in connection with the initial configuration. The winding degree tends to increase with initial angular speed provided that a disk is thin. If the disk surface is circular, both the number and position of arms are governed by the Poissonian density fluctuations that produce more arms as more particles are introduced. On the contrary, if the surface ellipticity is imposed, the number of arms and their placement are effectively controlled. Otherwise, the increase in thickness leads to a complicated outcome as the number of arms and winding degree are less effectively controlled. We speculate that this complexity is caused by a strong nonaxisymmetric field during the violent relaxation that disorganizes the precollapse motion and the concentration of particles.

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Long-lived transient structure in collisionless self-gravitating systems

Cited by 17 publications

References 63 publications

Gaia-DR2 extended kinematical maps

Gaia-DR2 extended kinematical maps

Gaia-DR2 extended kinematical maps

Formation of spiral structure from the violent relaxation of self‐gravitating disks

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