An ever-present Gaia snail shell triggered by a dark matter wake

Grand, Robert J J; Pakmor, Rüdiger; Fragkoudi, Francesca; Gómez, Facundo A; Trick, Wilma; Simpson, Christine M; van de Voort, Freeke; Bieri, Rebekka

Abstract

We utilize a novel numerical technique to model star formation in cosmological simulations of galaxy formation – called SUPERSTARS – to simulate a Milky Way-like galaxy with ≳108 star particles to study the formation and evolution of out-of-equilibrium stellar disc structures in a full cosmological setting. In the plane defined by the coordinate and velocity perpendicular to the mid-plane [vertical phase space, (Z, VZ)], stars in solar-like volumes at late times exhibit clear spirals qualitatively similar in shape and amplitude to the Gaia ‘snail shell’ phase spiral. We show that the phase spiral forms at a lookback time of ∼6 Gyr during the pericentric passage of an ∼1010M satellite on a polar orbit. This satellite stimulates the formation of a resonant wake in the dark matter halo while losing mass at a rate of ∼0.5–1 dex per orbit loop. The peak magnitude of the wake-induced gravitational torque at the solar radius is ∼8 times that from the satellite, and triggers the formation of a disc warp that wraps up into a vertical phase spiral over time. As the wake decays, the phase spiral propagates several gigayears to present day and can be described as ‘ever-present’ once stable disc evolution is established. These results suggest an alternative scenario to explain the Gaia phase spiral, which does not rely on a perturbation from bar buckling or a recent direct hit from a satellite.

Citation

Grand, R. J. J., Pakmor, R., Fragkoudi, F., Gómez, F. A., Trick, W., Simpson, C. M., …Bieri, R. (2023). An ever-present Gaia snail shell triggered by a dark matter wake. Monthly Notices of the Royal Astronomical Society, 524(1), 801-816. https://doi.org/10.1093/mnras/stad1969

• Journal Article Type: Article
• Acceptance Date: Jun 27, 2023
• Online Publication Date: Jun 30, 2023
• Publication Date: 2023-09
• Deposit Date: Dec 19, 2023
• Publicly Available Date: Dec 19, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 524
• Issue: 1
• Pages: 801-816
• DOI: https://doi.org/10.1093/mnras/stad1969
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://durham-repository.worktribe.com/output/2048293