Comparing hypervelocity star populations from the Large Magellanic Cloud and the Milky Way

Abstract

We predict and compare the distributions and properties of hyper-velocity stars (HVSs) ejected from the centres of the Milky Way (MW) and the Large Magellanic Cloud (LMC). In our model, HVSs are ejected at a constant rate -- equal in both galaxies -- via the Hills mechanism and are propagated in a combined potential, where the LMC orbits the MW on its first infall. By selecting $m>2{\mathrm{M}}_{\odot }$ HVSs well-separated from the Magellanic Clouds and Galactic midplane, we identify mock HVSs which would stand out from ordinary stars in the stellar halo in future data releases from the Gaia satellite and the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). We find that in these deep surveys, LMC HVSs will outnumber MW ones by a factor $\sim 2.5$, as HVSs can more easily escape from the shallower potential of the LMC. At an assumed HVS ejection rate of $10^{-4}\mathrm{y}{\mathrm{r}}^{-1}$, HVSs detectable in the final Gaia data release and LSST from the LMC (MW) will number $125_{-12}^{+11}$ ($50_{-8}^{+7}$) and $140_{-11}^{+10}$ ($42_{-7}^{+6}$), respectively. The MW and LMC HVS populations show different kinematics and spatial distributions. While LMC HVSs have more modest total velocities and larger Galactocentric distances clustered around those of the LMC itself, HVSs from the MW show broader distributions, including a prominent high-velocity tail above $500\mathrm{km}{\mathrm{s}}^{-1}$ that contains at least half of the stars. These predictions are robust against reasonable variation of the Galactic potential and of the LMC central black hole mass.

18 pages, 10 figures. Accepted for publication in MNRAS

References in corpus (33)

• The Gaia mission
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• galpy: A Python Library for Galactic Dynamics
• The mass distribution and gravitational potential of the Milky Way
• An eclipsing binary distance to the Large Magellanic Cloud accurate to 2 per cent
• Are the Magellanic Clouds on their First Passage about the Milky Way?
• Measurement of the rate of stellar tidal disruption flares
• Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33
• Hidden AGN in dwarf galaxies revealed by MaNGA: light echoes, off-nuclear wanderers, and a new broad-line AGN
• Hypervelocity Stars: From the Galactic Center to the Halo
• An Alternative Origin for Hypervelocity Stars
• A Successful Targeted Search for Hypervelocity Stars
• KMOS view of the Galactic Centre - II. Metallicity distribution of late-type stars
• Maximum speed of hypervelocity stars ejected from binaries
• Reflex motion in the Milky Way stellar halo resulting from the Large Magellanic Cloud infall
• Completeness of the Gaia-verse II: what are the odds that a star is missing from Gaia DR2?
• A semi-analytic dynamical friction model for cored galaxies
• Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
• Predicted Space Motions for Hypervelocity and Runaway Stars: Proper Motions and Radial Velocities for the GAIA Era
• LMC origin of the hyper-velocity star HE 0437-5439. Beyond the supermassive black hole paradigm
• The Pisces Plume and the Magellanic Wake
• The Complete Initial Mass Function Down to the Sub-Solar Regime in the Large Magellanic Cloud with Hubble Space Telescope ACS Observations
• Inferring the gravitational potential of the Milky Way with a few precisely measured stars
• The Anisotropic Spatial Distribution of Hypervelocity Stars
• Detailed Abundances for the Old Population near the Galactic Center: I. Metallicity distribution of the Nuclear Star Cluster
• Discovery of two new hypervelocity stars from the LAMOST spectroscopic surveys
• Joint constraints on the Galactic dark matter halo and Galactic Centre from hypervelocity stars
• Hypervelocity Stars from the Andromeda Galaxy
• Core-Collapse Supernovae in Binaries as the Origin of Galactic Hyper-Runaway Stars
• Gaia EDR3 in 6D: Searching for unbound stars in the Galaxy
• The Nearest High-Velocity Stars Revealed by LAMOST Data Release 1
• Completeness of the Gaia-verse I: when and where were Gaia's eyes on the sky during DR2?
• An artificial neural network to discover Hypervelocity stars: Candidates in Gaia DR1/TGAS