All-Sky Kinematics of the Distant Halo: The Reflex Response to the LMC

Abstract

The infall of the Large Magellanic Cloud (LMC) is predicted to displace the inner Milky Way (MW), imprinting an apparent 'reflex motion' on the observed velocities of distant halo stars. We construct the largest all-sky spectroscopic dataset of luminous red giant stars from $50-160$ kpc, including a new survey of the southern celestial hemisphere. We fit the full 6D kinematics of our data to measure the amplitude and direction of the inner MW's motion towards the outer halo. The observed velocity grows with distance such that, relative to halo stars at $100$ kpc, the inner MW is lurching at $\approx 40$ km s${}^{-1}$ towards a recent location along the LMC's past orbit. Our measurements align with N-body simulations of the halo's response to a $1.8\times 10^{11}{M}_{\odot }$ LMC on first infall, suggesting that the LMC is at least 15% as massive as the MW. Our findings highlight the dramatic disequilibrium of the MW outskirts, and will enable more accurate measurements of the total mass of our Galaxy.

arXiv comment32 pages, 22 figures. Accepted to ApJ

References in corpus (87)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The Sloan Digital Sky Survey: Technical Summary
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Seventh Data Release of the Sloan Digital Sky Survey
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• The observed properties of dwarf galaxies in and around the Local Group
• The Sloan Digital Sky Survey Photometric Camera
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• Gaia Early Data Release 3: The astrometric solution
• SEGUE: A Spectroscopic Survey of 240,000 stars with g=14-20
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: I. Morphology of the Sagittarius Core and Tidal Arms
• Co-formation of the Galactic disc and the stellar halo
• Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole
• The Proper Motion of Sgr A*: II. The Mass of Sgr A*
• Initial Performance of the NEOWISE Reactivation Mission
• Stellar Population Inference with Prospector
• Are the Magellanic Clouds on their First Passage about the Milky Way?
• The Sagittarius Dwarf Galaxy: a Model for Evolution in a Triaxial Milky Way Halo
• Gaia EDR3 view on Galactic globular clusters
• Third-Epoch Magellanic Cloud Proper Motions I: HST/WFC3 data and Orbit Implications
• The unWISE Catalog: Two Billion Infrared Sources from Five Years of WISE Imaging
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• The total mass of the Large Magellanic Cloud from its perturbation on the Orphan stream
• The Proper Motion of the Large Magellanic Cloud using HST
• Tango for three: Sagittarius, LMC, and the Milky Way
• Stars beyond Galaxies: The Origin of Extended Luminous Halos around Galaxies
• The Origin of the Magellanic Stream and Its Leading Arm
• Simulations of the Magellanic Stream in a First Infall Scenario
• Assessing the Milky Way Satellites Associated with the Sagittarius Dwarf Spheroidal Galaxy
• The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater
• A timing constraint on the (total) mass of the Large Magellanic Cloud
• A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters
• Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud
• The Causes of Halo Shape Changes Induced by Cooling Baryons: Disks Versus Substructures
• The distribution and kinematics of early high-sigma peaks in present-day haloes: implications for rare objects and old stellar populations
• The MagE Spectrograph
• Contributions to the accreted stellar halo: an atlas of stellar deposition
• And yet it moves: The dangers of artificially fixing the Milky Way center of mass in the presence of a massive Large Magellanic Cloud
• The Global Dynamical Atlas of the Milky Way mergers: Constraints from Gaia EDR3 based orbits of globular clusters, stellar streams and satellite galaxies
• Mapping the Stellar Halo with the H3 Spectroscopic Survey
• Overview of the DESI Milky Way Survey
• Response of the Milky Way's disc to the Large Magellanic Cloud in a first infall scenario
• The mass of our Milky Way
• The radial profile and flattening of the Milky Way's stellar halo to $80$kpc from the SEGUE K-giant Survey
• Quantifying the impact of the Large Magellanic Cloud on the structure of the Milky Way's dark matter halo using Basis Function Expansions
• A box full of chocolates: The rich structure of the nearby stellar halo revealed by Gaia and RAVE
• Measuring the Mass of the Large Magellanic Cloud with Stellar Streams Observed by $S^5$
• All-Sky Dynamical Response of the Galactic Halo to the Large Magellanic Cloud
• Detection of the Milky Way reflex motion due to the Large Magellanic Cloud infall
• $S^5$: Probing the Milky Way and Magellanic Clouds potentials with the 6-D map of the Orphan-Chenab stream
• Detection of the LMC-induced sloshing of the Galactic halo
• Satellite Galaxies and Fossil Groups in the Millennium Simulation
• Stellar streams around the Magellanic Clouds
• Reflex motion in the Milky Way stellar halo resulting from the Large Magellanic Cloud infall
• The slight spin of the old stellar halo
• A hypervelocity star with a Magellanic origin
• Production of Milky Way structure by the Magellanic Clouds
• The effect of the LMC on the Milky Way system
• Equilibrium models of the Milky Way mass are biased high by the LMC
• The effect of the deforming dark matter haloes of the Milky Way and the Large Magellanic Cloud on the Orphan-Chenab stream
• MINESweeper: Spectrophotometric Modeling of Stars in the Gaia Era
• The Stellar Halo of the Galaxy is Tilted & Doubly Broken
• The Pisces Plume and the Magellanic Wake
• The Origin of the Microlensing Events Observed Towards the LMC and the Stellar Counterpart of the Magellanic Stream
• Quantifying the Stellar Halo's Response to the LMC's Infall with Spherical Harmonics
• Measuring the slopes of mass profiles for dwarf spheroidals in triaxial CDM potentials
• HALO7D II: The Halo Velocity Ellipsoid and Velocity Anisotropy with Distant Main Sequence Stars
• Discovery of the Magellanic Stellar Stream Out to 100 Kiloparsecs
• Implications of the Milky Way travel velocity for dynamical mass estimates of the Local Group
• Distant Echoes of the Milky Way's Last Major Merger
• Beta Dips in the Gaia Era: Simulation Predictions of the Galactic Velocity Anisotropy Parameter for Stellar Halos
• Revisiting dynamical friction: the role of global modes and local wakes
• Mapping the anisotropic Galactic stellar halo with Blue Horizontal Branch stars
• Identification of Sagittarius stream members in Angular Momentum space with Gaussian mixture techniques
• Structure, Kinematics, and Observability of the Large Magellanic Cloud's Dynamical Friction Wake in Cold vs. Fuzzy Dark Matter
• Tidally stripped halo stars from the Large Magellanic Cloud in the Galactic North
• Discovery of Magellanic Stellar Debris in the H3 Survey
• Value-added catalog of M-giant stars in LAMOST DR9
• Effect of the Large Magellanic Cloud on the kinematics of Milky Way satellites and virial mass estimate
• A Catalog of Distance Determinations for the LAMOST DR8 K Giants in the Galactic Halo
• A determination of the LMC dark matter subhalo mass using the MW halo stars in its gravitational wake
• A history of the Magellanic Clouds and the European exploration of the Southern Hemisphere

Cited by in corpus (8)

• Following the tidal trail: a history of modeling the Magellanic Stream
• Mapping the Distant and Metal-Poor Milky Way with SDSS-V
• A Simulation Based Inference Approach to the Dynamics of the MW-LMC System -- Validation
• Quantifying the Milky Way, LMC and their interaction using all-sky kinematics of outer halo stars
• Mapping the Distorted Dark Matter Distribution of the LMC-SMC System Prior to Milky Way Infall with Basis Function Expansions
• The mass distribution in and around the Local Group
• GSE vs. LMC: reshaping of radially biased stellar haloes by satellites
• The orbital dynamics of the LMC and SMC about the Milky Way