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Gaia has revealed a clear signal of disequilibrium in the solar neighborhood in the form of a spiral (or snail) feature in the vertical phase-space distribution. We investigate the possibility that this structure emerges from ongoing…

Astrophysics of Galaxies · Physics 2025-01-30 Daniel Gilman , Jo Bovy , Neige Frankel , Andrew Benson

The distribution of stars in the Milky Way disc shows a spiral structure--the Snail--in the space of velocity and position normal to the Galactic mid-plane. The Snail appears as straight lines in the vertical frequency--vertical phase plane…

Astrophysics of Galaxies · Physics 2023-04-05 Neige Frankel , Jo Bovy , Scott Tremaine , David W. Hogg

The Galaxy is found to be in disequilibrium based on recent findings of the North/South (N/S) asymmetry and the phase mixing signatures, such as a phase spiral (snail) structure in the vertical phase space ($z-V_{z}$). We show that the N/S…

Astrophysics of Galaxies · Physics 2022-09-14 Rui Guo , Juntai Shen , Zhao-yu Li , Chao Liu , Shude Mao

The perturbation mechanism of the Galactic disk has puzzled us for a long time. The imprints from perturbations provide important diagnostics on the disk formation and evolution. Here we try to constrain when the vertical perturbation took…

Astrophysics of Galaxies · Physics 2018-10-10 Hai-Jun Tian , Chao Liu , Yue Wu , Mao-Sheng Xiang , Yong Zhang

The Gaia snail is a spiral feature in the distribution of solar-neighbourhood stars in position and velocity normal to the Galactic midplane. The snail probably arises from phase mixing of gravitational disturbances that perturbed the disc…

Astrophysics of Galaxies · Physics 2023-03-01 Scott Tremaine , Neige Frankel , Jo Bovy

The distribution of chemical elements in the Galactic disc can reveal fundamental clues on the physical processes that led to the current configuration of our Galaxy. We map chemical azimuthal variations in the disc using individual stellar…

Astrophysics of Galaxies · Physics 2024-12-25 M. Barbillon , A. Recio-Blanco , E. Poggio , P. A. Palicio , E. Spitoni , P. de Laverny , G. Cescutti

In 2018, the ESA \Gaia\ satellite discovered a remarkable spiral pattern ("phase spiral") in the $z-V_z$ phase plane throughout the solar neighbourhood, where $z$ and $V_z$ are the displacement and velocity of a star perpendicular to the…

Astrophysics of Galaxies · Physics 2021-03-17 Joss Bland-Hawthorn , Thor Tepper-Garcia

The phase spiral is a perturbation to the vertical phase-space distribution of stars in the Milky Way disk. We study the phase spiral's properties and how they vary with spatial position, in order to constrain its origin and evolution, as…

Astrophysics of Galaxies · Physics 2025-07-29 Axel Widmark , Kiyan Tavangar , Josh Kalish , Kathryn V. Johnston , Jason A. S. Hunt

The Gaia satellite revealed a remarkable spiral pattern ('phase spiral', PS) in the z-Vz phase-plane throughout the solar neighbourhood, where z and Vz are the displacement and velocity of a star perpendicular to the Galactic plane. As…

Astrophysics of Galaxies · Physics 2025-08-21 Thor Tepper-García , Joss Bland-Hawthorn , Timothy R. Bedding , Christoph Federrath , Oscar Agertz

By combining the {\it LAMOST} and {\it Gaia} data, we investigate the vertical phase mixing across the Galactic disk. Our results confirm the existence of the phase space snail shells (or phase spirals) from 6 to 12 kpc. We find that…

Astrophysics of Galaxies · Physics 2021-04-28 Zhao-Yu Li

We test whether the spiral patterns apparent in many large disk galaxies should be thought of as dynamical features that are stationary in a co-rotating frame for > t_{dyn}, as implied by the density wave approach for explaining spiral…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Kelly Foyle , Hans-Walter Rix , Clare Dobbs , Adam Leroy , Fabian Walter

The density-wave theory of spiral structure proposes that star formation occurs in or near a spiral-shaped region of higher density that rotates rigidly within the galactic disk at a fixed pattern speed. In most interpretations of this…

We study the links between star formation history and structure for a large mass-selected galaxy sample at 0.05 < z_phot < 0.30. The galaxies inhabit a very broad range of environments, from cluster cores to the field. Using HST images, we…

Recent studies have shown that the passage of a massive satellite through the disk of a spiral galaxy can induce vertical wobbles in the disk and produce features such as in-plane rings and phase-space spirals. Here we analyze a…

Astrophysics of Galaxies · Physics 2019-07-10 Tim Haines , Elena D'Onghia , Benoit Famaey , Chervin Laporte , Lars Hernquist

Many approaches to galaxy dynamics assume that the gravitational potential is simple and the distribution function is time-invariant. Under these assumptions there are traditional tools for inferring potential parameters given observations…

The evolution of the Milky Way disk, which contains most of the stars in the Galaxy, is affected by several phenomena. For example, the bar and the spiral arms of the Milky Way induce radial migration of stars and can trap or scatter stars…

Gaia has revealed a variety of substructures in the phase space of stars in the Solar neighborhood, including the vertical `Snail' in $(z,v_z)$ space. Such substructures are often interpreted as the incompletely phase-mixed response of the…

Astrophysics of Galaxies · Physics 2025-10-22 Rimpei Chiba , Jupiter Ding , Chris Hamilton , Matthew W. Kunz , Scott Tremaine

We discuss the physical mechanism by which pure vertical bending waves in a stellar disc evolve to form phase space spirals similar to those discovered by Antoja et al. ( arXiv:1804.10196) in Gaia Data Release 2. These spirals were found by…

Astrophysics of Galaxies · Physics 2019-01-01 Keir Darling , Lawrence M. Widrow

Matter distribution models of the Milky Way galaxy are usually stationary, although there are known to be wave-like perturbations in the disc at $\sim10\%$ level of the total density. Modelling of the overall acceleration field by allowing…

Astrophysics of Galaxies · Physics 2021-08-18 Rain Kipper , Peeter Tenjes , Elmo Tempel , Roberto de Propris

Stellar chemical compositions can be altered by ingestion of planetary material and/or planet formation which removes refractory material from the proto-stellar disc. These "planet signatures" appear as correlations between elemental…

Solar and Stellar Astrophysics · Physics 2024-03-21 Fan Liu , Yuan-Sen Ting , David Yong , Bertram Bitsch , Amanda Karakas , Michael T. Murphy , Meridith Joyce , Aaron Dotter , Fei Dai
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