Self-Perpetuating Spiral Arms in Disk Galaxies

D’Onghia, Elena; Vogelsberger, Mark; Hernquist, Lars

doi:10.1088/0004-637x/766/1/34

Cited by 243 publications

(240 citation statements)

References 40 publications

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“…In recent years, it was found that the nonlinear effect is significant to understand the overall activity of the spiral arms (e.g., Baba et al 2013;D'Onghia et al 2013). We found that the linear theory can predict the correct pitch angle that is consistent with the numerical simulation.…”

Section: Resultssupporting

confidence: 78%

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Pitch Angle of Galactic Spiral Arms

Michikoshi

Kokubo

2014

ApJ

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One of the key parameters that characterizes 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 that the rotation law of galactic disks determines it. In order to investigate the relation between the pitch angle of spiral arms and the shear rate of galactic differential rotation, we perform local N-body simulations of pure stellar disks. We find that the pitch angle increases with the epicycle frequency and decreases with the shear rate and obtain the fitting formula. This dependence is explained by the swing amplification mechanism.

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Section: Resultssupporting

confidence: 78%

“…This indicates that the leading mode is always generated. We do not discuss the origin of the leading mode here, but it may be generated by some nonlinear processes (e.g., Fuchs et al 2005;D'Onghia et al 2013). The overall evolution of spiral arms cannot be obtained by the linear theory.…”

Section: Linear Analysismentioning

confidence: 99%

Pitch Angle of Galactic Spiral Arms

Michikoshi

Kokubo

2014

ApJ

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“…Finally, this research field has been recently boosted by numerical simulations. N-body solvers are achieving higher and higher resolution and although they are still missing a complete self-consistent understanding of the spiral arm dynamics, several numerical techniques (e.g., the tree-code, Barnes & Hut 1986) allow us to simulate the gravitational interactions among millions of particles with masses of the order of a few thousand solar masses or less (D'Onghia, Vogelsberger & Hernquist 2013;Grand, Kawata & Cropper 2012b,a).…”

Section: Observational Studies Of Density Wave Theorymentioning

confidence: 99%

Spiral arm kinematics for Milky Way stellar populations

Pasetto

Natale

Kawata

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a new theoretical population synthesis model (the Galaxy Model) to examine and deal with large amounts of data from surveys of the Milky Way and to decipher the present and past structure and history of our own Galaxy.We assume the Galaxy to consist of a superposition of many composite stellar populations belonging to the thin and thick disks, the stellar halo and the bulge, and to be surrounded by a single dark matter halo component. A global model for the Milky Way's gravitational potential is built up self-consistently with the density profiles from the Poisson equation. In turn, these density profiles are used to generate synthetic probability distribution functions (PDFs) for the distribution of stars in colour-magnitude diagrams (CMDs). Finally, the gravitational potential is used to constrain the stellar kinematics by means of the moment method on a (perturbed)-distribution function. Spiral arms perturb the axisymmetric disk distribution functions in the linear response framework of density-wave theory where we present an analytical formula of the so-called 'reduction factor' using Hypergeometric functions.Finally, we consider an analytical non-axisymmetric model of extinction and an algorithm based on the concept of probability distribution function to handle colour magnitude diagrams with a large number of stars. A genetic algorithm is presented to investigate both the photometric and kinematic parameter space.This galaxy model represents the natural framework to reconstruct the structure of the Milky Way from the heterogeneous data set of surveys such as Gaia-ESO, SEGUE, APOGEE2, RAVE and the Gaia mission.

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“…In the last description, spiral arms are transient, recurrent features that wind up and disappear with time, continually being replaced by new transient features that form from small perturbations amplified by a mechanism akin to swing amplification (Goldreich & Lynden-Bell 1965;Julian & Toomre 1966;Toomre 1981;D'Onghia et al 2013). These structures are found to be approximately co-rotating with the disc stars at every radius (e.g., Grand et al 2012a,b), and cause continual radial migration at every radius that manifests as large systematic streaming motions along the spiral arm Hunt et al 2015), which is expected to be different from the peculiar motions induced by density wave spirals.…”

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confidence: 99%

Spiral- and bar-driven peculiar velocities in Milky Way-sized galaxy simulations

Grand

Bovy

Kawata

et al. 2015

Mon. Not. R. Astron. Soc.

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We investigate the kinematic signatures induced by spiral and bar structure in a set of simulations of Milky Way-sized spiral disc galaxies. The set includes test particle simulations that follow a quasi-stationary density wave-like scenario with rigidly rotating spiral arms, and N -body simulations that host a bar and transient, co-rotating spiral arms. From a location similar to that of the Sun, we calculate the radial, tangential and line-of-sight peculiar velocity fields of a patch of the disc and quantify the fluctuations by computing the power spectrum from a two-dimensional Fourier transform. We find that the peculiar velocity power spectrum of the simulation with a bar and transient, co-rotating spiral arms fits very well to that of APOGEE red clump star data, while the quasi-stationary density wave spiral model without a bar does not. We determine that the power spectrum is sensitive to the number of spiral arms, spiral arm pitch angle and position with respect to the spiral arm. However, it is necessary to go beyond the line of sight velocity field in order to distinguish fully between the various spiral models with this method. We compute the power spectrum for different regions of the spiral discs, and discuss the application of this analysis technique to external galaxies.

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Self-Perpetuating Spiral Arms in Disk Galaxies

Cited by 243 publications

References 40 publications

Pitch Angle of Galactic Spiral Arms

Pitch Angle of Galactic Spiral Arms

Spiral arm kinematics for Milky Way stellar populations

Spiral- and bar-driven peculiar velocities in Milky Way-sized galaxy simulations

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