Snails Across Scales: Local and Global Phase-Mixing Structures as Probes of the Past and Future Milky Way

Abstract

Signatures of vertical disequilibrium have been observed across the Milky Way's disk. These signatures manifest locally as unmixed phase-spirals in $z$--$v_z$ space ("snails-in-phase") and globally as nonzero mean $z$ and $v_z$ which wraps around as a physical spiral across the $x$--$y$ plane ("snails-in-space"). We explore the connection between these local and global spirals through the example of a satellite perturbing a test-particle Milky Way (MW)-like disk. We anticipate our results to broadly apply to any vertical perturbation. Using a $z$--$v_z$ asymmetry metric we demonstrate that in test-particle simulations: (a) multiple local phase-spiral morphologies appear when stars are binned by azimuthal action $J_{\varphi }$, excited by a single event (in our case, a satellite disk-crossing); (b) these distinct phase-spirals are traced back to distinct disk locations; and (c) they are excited at distinct times. Thus, local phase-spirals offer a global view of the MW's perturbation history from multiple perspectives. Using a toy model for a Sagittarius (Sgr)-like satellite crossing the disk, we show that the full interaction takes place on timescales comparable to orbital periods of disk stars within $R\lesssim 10$ kpc. Hence such perturbations have widespread influence which peaks in distinct regions of the disk at different times. This leads us to examine the ongoing MW-Sgr interaction. While Sgr has not yet crossed the disk (currently, $z_{Sgr}\approx -6$ kpc, $v_{z,Sgr}\approx 210$ km/s), we demonstrate that the peak of the impact has already passed. Sgr's pull over the past 150 Myr creates a global $v_z$ signature with amplitude $\propto M_{Sgr}$, which might be detectable in future spectroscopic surveys.

References in corpus (52)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• Gaia Data Release 2. Summary of the contents and survey properties
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• The SIMBAD astronomical database
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The observed properties of dwarf galaxies in and around the Local Group
• galpy: A Python Library for Galactic Dynamics
• The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• The Radial Velocity Experiment (RAVE): first data release
• The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS
• The Ghost of Sagittarius and Lumps in the Halo of the Milky Way
• A dynamically young and perturbed Milky Way disk
• The Kinematics, Orbit, and Survival of the Sagittarius Dwarf Spheroidal Galaxy
• Galactoseismology: Discovery of Vertical Waves in the Galactic Disk
• Footprints of the Sagittarius dwarf galaxy in the $Gaia$ data set
• The wobbly Galaxy: kinematics north and south with RAVE red clump giants
• Equilibrium Disk-Bulge-Halo Models for the Milky Way and Andromeda Galaxies
• Rings and Radial Waves in the Disk of the Milky Way
• Vertical density waves in the Milky Way disc induced by the Sagittarius Dwarf Galaxy
• The Influence of Sagittarius and the Large Magellanic Cloud on the Milky Way Galaxy
• The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry and location
• A sparse octree gravitational N-body code that runs entirely on the GPU processor
• Distribution functions for the Milky Way
• Response of the Milky Way's disc to the Large Magellanic Cloud in a first infall scenario
• Bending and Breathing Modes of the Galactic Disk
• The origin of the Gaia phase-plane spiral
• Substructure in bulk velocities of Milky Way disk stars
• Warp, Waves, and Wrinkles in the Milky Way
• Radial Distribution of Stellar Motions in Gaia DR2
• The echo of the bar buckling: phase-space spirals in Gaia DR2
• The Galactic warp revealed by Gaia DR2 kinematics
• Galactic seismology: the evolving "phase spiral" after the Sagittarius dwarf impact
• The last breath of the Sagittarius dSph
• A re-interpretation of the Triangulum-Andromeda stellar clouds: a population of halo stars kicked out of the Galactic disk
• Signatures of resonance and phase mixing in the Galactic disc
• Evidence of a dynamically evolving Galactic warp
• Two chemically similar stellar overdensities on opposite sides of the plane of the Galaxy
• Emergence of the Gaia Phase Space Spirals from Bending Waves
• Bending Waves in the Milky Way's disc from halo substructure
• More than just a wrinkle: A wave-like pattern in radial velocity vs. angular momentum from Gaia Data
• A Disk Origin for the Monoceros Ring and A13 Stellar Overdensities
• Kinematics and dynamics of Gaia red clump stars
• Time stamps of vertical phase mixing in the Galactic disk from LAMOST-Gaia stars
• Exploring the pertubed Milky Way disk and the substructures of the outer disk
• Spontaneous generation of bending waves in isolated Milky Way-like discs
• Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum-Andromeda Overdensity?
• Did Sgr cause the vertical waves in the solar neighbourhood?
• Vertical Phase Mixing across the Galactic Disk
• The power of co-ordinate transformations in dynamical interpretations of Galactic structure

Cited by in corpus (14)

• Galactic Archaeology with Gaia
• Multiple phase spirals suggest multiple origins in Gaia DR3
• The phase spiral in Gaia DR3
• Vertical motion in the Galactic disc: unwinding the Snail
• A Comprehensive Perturbative Formalism for Phase-Mixing in Perturbed Disks. I. Phase spirals in an Infinite, Isothermal Slab
• Radial phase spirals in the Solar neighbourhood
• A Comprehensive Perturbative Formalism for Phase Mixing in Perturbed Disks. II. Phase Spirals in an Inhomogeneous Disk Galaxy with a Non-responsive Dark Matter Halo
• 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
• Radial Wave in the Galactic Disk: New Clues to Discriminate Different Perturbations
• A barred Milky Way surrogate from an N-body simulation
• Two-point correlation function studies for the Milky Way: discovery of spatial clustering from disk excitations and substructure
• Delayed phase mixing in the self-gravitating Galactic disc
• The disturbed outer Milky Way disc