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

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 $\gtrsim 10^8$ 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, $\{Z,V_Z\}$), 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 look back time of $\sim 6$ Gyr during the pericentric passage of a $\sim 10^{10}$ ${\mathrm{M}}_{\odot }$ 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 $\sim 0.5$-$1$ dex per orbit loop. The peak magnitude of the wake-induced gravitational torque at the Solar radius is $\sim 8$ 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.

accepted for pub in mnras. 11 + 5 pages. For a high-cadence animated version of figure 1, see https://wwwmpa.mpa-garching.mpg.de/auriga/movies/multi_halo_6_sf64.mp4

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Cited by in corpus (13)

• Gaia DR3 features of the phase spiral and its possible relation to internal perturbations
• The Great Wave: Evidence of a large-scale vertical corrugation propagating outwards in the Galactic disc
• Radial phase spirals in the Solar neighbourhood
• Investigating the amplitude and rotation of the phase spiral in the Milky Way outer disc
• Ripples spreading across the Galactic disc. Interplay of direct and indirect effects of the Sagittarius dwarf impact
• Shaping the Milky Way: The interplay of mergers and cosmic filaments
• Auriga Streams I: disrupting satellites surrounding Milky Way-mass haloes at multiple resolutions
• Limitations and rotation of the two-armed phase spiral in the Milky Way stellar disc
• Delayed phase mixing in the self-gravitating Galactic disc
• Auriga Superstars: Improving the resolution and fidelity of stellar dynamics in cosmological galaxy simulations
• Stirring Things Up: Bar-induced substructures in the stellar halo of a cosmological Milky Way analogue
• Wrinkles in Time. II. Stellar Age Trends in Kinematic Signatures from Transient Spiral Structure
• Phase spirals induced by the gas warp