Bending and breathing modes of the Galactic disc

Widrow, Lawrence M.; Barber, Jarrett J.; Chequers, Matthew H.; Cheng, E. S.

doi:10.1093/mnras/stu396

Cited by 145 publications

(199 citation statements)

References 66 publications

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“…As a satellite galaxy passes through the disk, it excites both bending and breathing modes (Widrow et al 2014). The former have been implicated in the generation of galactic warps.…”

Section: Discussionmentioning

confidence: 99%

“…Our N-body system comprises self-gravitating, collisionless infinite sheets. We use a particle-mesh scheme in which the density is calculated on a one-dimensional grid and the force on a sheet at position z is determined from the integral Similar simulations were presented in Weinberg (1991); Widrow et al (2012) and Widrow et al (2014). We use initial conditions that correspond to a simple breathing mode by first setting up an equlibrium distribution and then perturbing the positions and velocities according to the relations z = λzze and v = λvve where (ze, ve) are the phase space coordinates of a particle in the unperturbed system and λe,v are constants.…”

Section: Simulationsmentioning

confidence: 99%

“…Velocity and number density perturbations normal to the Galactic midplane can result from satellite-disk interactions (Widrow et al 2012;Gómez et al 2013;Widrow et al 2014). Gómez et al (2013), for example, used N-body experiments to show that a Sagittarius-like dwarf with a mass of 10 10.5 − 10 11 M⊙ could produce density perturbations of the same amplitude as was seen in Widrow et al (2012) and Yanny & Gardner (2013).…”

Section: Introductionmentioning

confidence: 99%

“…Widrow et al (2014) followed the evolution of bending and breathing modes in the Gauthier et al (2006) simulation, where the disk was subjected to the continual perturbations of a substructure-filled halo. Bending and breathing modes appear at early times as subhalos churn up the disk.…”

Section: Introductionmentioning

confidence: 99%

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Vertical oscillations of fluid and stellar discs

Widrow

Bonner

2015

Monthly Notices of the Royal Astronomical Society

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A satellite galaxy or dark matter subhalo that passes through a stellar disk may excite coherent oscillations in the disk perpendicular to its plane. We determine the properties of these modes for various self-gravitating plane symmetric systems (Spitzer sheets) using the matrix method of Kalnajs. In particular, we find an infinite series of modes for the case of a barotropic fluid. In general, for a collisionless system, there is a double series of modes, which include normal modes and/or Landau-damped oscillations depending on the phase space distribution function of the stars. Even Landau-damped oscillations may decay slowly enough to persist for several hundred Myr. We discuss the implications of these results for the recently discovered vertical perturbations in the kinematics of solar neighborhood stars and for broader questions surrounding secular phenomena such as spiral structure in disk galaxies.

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“…As a satellite galaxy passes through the disk, it excites both bending and breathing modes (Widrow et al 2014). The former have been implicated in the generation of galactic warps.…”

Section: Discussionmentioning

confidence: 99%

Section: Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Vertical oscillations of fluid and stellar discs

Widrow

Bonner

2015

Monthly Notices of the Royal Astronomical Society

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“…These motions may be induced by external perturbations, such as a satellite galaxy, (e.g. Widrow et al 2014) or internal perturbations, such as spiral arms (e.g. Faure et al 2014).…”

Section: Determination Of Galactocentric Positions and Velocitiesmentioning

confidence: 99%

TheGaia-ESO Survey: characterisation of the [α/Fe] sequences in the Milky Way discs

Kordopatis

Wyse

Gilmore

et al. 2015

A&A

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Context. High-resolution spectroscopic surveys of stars indicate that the Milky Way thin and thick discs follow different paths in the chemical space defined by [α/Fe] vs. [Fe/H], possibly suggesting different formation mechanisms for each of these structures. Aims. We investigate, using the Gaia-ESO Survey internal Data-Release 2, the properties of the double sequence of the Milky Way discs, which are defined chemically as the high-α and low-α populations. We discuss their compatibility with discs defined by other means, such as metallicity, kinematics, or positions. Methods. This investigation uses two different approaches: in velocity space, for stars located in the extended solar neighbourhood; and, in chemical space, for stars at different ranges of Galactocentric radii and heights from the Galactic mid-plane. The separation we find in velocity space allows us to investigate, using a novel approach, the extent of metallicity of each of the two chemical sequences, without making any assumption about the shape of their metallicity distribution functions. Then, using the separation in chemical space, adopting the magnesium abundance as a tracer of the α-elements, we characterise the spatial variation of the slopes of the [α/Fe]−[Fe/H] sequences for the thick and thin discs and the way in which the relative proportions of the two discs change across the Galaxy. Results. We find that the thick disc, defined as the stars tracing the high-α sequence, extends up to super-solar metallicities ([Fe/H] ≈ +0.2 dex), and the thin disc, defined as the stars tracing the low-α sequence, extends at least down to [Fe/H] ≈ −0.8 dex, with hints pointing towards even lower values. Radial and vertical gradients in α-abundances are found for the thin disc, with mild spatial variations in its [α/Fe]−[Fe/H] paths, whereas for the thick disc we do not detect any spatial variations of this kind. This is in agreement with results obtained recently from other high-resolution spectroscopic surveys. Conclusions. The small variations in the spatial [α/Fe]−[Fe/H] paths of the thin disc do not allow us to distinguish between formation models of this structure. On the other hand, the lack of radial gradients and [α/Fe]−[Fe/H] variations for the thick disc indicate that the mechanism responsible for the mixing of metals in the young Galaxy (e.g. radial stellar migration or turbulent gaseous disc) was more efficient before the (present) thin disc started forming.

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The Milky Way disk non‐axisymmetries and galactoseismology

2016

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Current Galactic dynamical models still most often rely on the assumptions of a smooth time-independent and axisymmetric gravitational potential. On the other hand, ab initio simulations in a cosmological context are not very flexible to precisely produce a model of our own Galaxy, or to disentangle the internal and the external/environmental effects on its evolution. To make such a disentanglement possible, one can first try to isolate all the possible effects of one main nonaxisymmetric perturber, such as the bar or the spiral arms, through perturbation theory applied to smooth time-independent axisymmetric potentials. For instance, it has recently been realized in this way that observed vertical oscillations of the Galactic disk could be due to such internal perturbations, rather than to external perturbers as previously believed. Here we summarize the general analytical framework, in the context of perturbation theory, which allowed us to compute the stellar vertical bulk motions generated by a single internal perturber such as the Galactic bar. We point out that non-linear couplings can nevertheless be present when multiple non-axisymmetric perturbers -such as multiple spiral patterns together with a central bar -are present simultaneously, thus potentially enhancing the effect presented here.

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Bending and breathing modes of the Galactic disc

Cited by 145 publications

References 66 publications

Vertical oscillations of fluid and stellar discs

Vertical oscillations of fluid and stellar discs

TheGaia-ESO Survey: characterisation of the [α/Fe] sequences in the Milky Way discs

The Milky Way disk non‐axisymmetries and galactoseismology

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