Searching for stars ejected from the Galactic Centre in DESI

Abstract

Dynamical interactions between stars and the super massive black hole Sgr A* at the Galactic Centre (GC) may eject stars into the Galactic halo. While recent fast ejections by Sgr A* have been identified in the form of hypervelocity stars (hundreds to thousands km/s), it is also expected that the stellar halo contains slower stars, ejected over the last few billion years. In this study, we use the first data release of DESI to search for these slower GC ejecta, which are expected to stand out from the stellar halo population for their combined high metallicity ($[Fe/H]\gtrsim 0$) and small values of their vertical angular momentum ($L_Z$), whose distribution should peak at zero. Our search does not yield a detection, but allows us to place an upper limit on the ejection rate of stars from the GC of $\sim 2.8\times 10^{-3}$ yr${}^{-1}$ over the past ~5 Gyr, which is ejection model independent. This implies that our result can be used to put constraints on different ejection models, including that invoking mergers of Sgr A* with other massive black holes in the last last few billion years.

7 pages, 5 figures, accepted in A&A

References in corpus (58)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The Gaia mission
• 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
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• MESA Isochrones and Stellar Tracks (MIST). I: Solar-Scaled Models
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• The Galaxy in Context: Structural, Kinematic and Integrated Properties
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• The mass distribution and gravitational potential of the Milky Way
• Co-formation of the Galactic disc and the stellar halo
• AGAMA: Action-based galaxy modelling architecture
• Evidence for Two Early Accretion Events That Built the Milky Way Stellar Halo
• The accretion origin of the Milky Way's stellar halo
• Ejection of hypervelocity stars by the (binary) black hole(s) in the Galactic center
• Discovery of an Unbound Hyper-Velocity Star in the Milky Way Halo
• In disguise or out of reach: first clues about in-situ and accreted stars in the stellar halo of the Milky Way from Gaia DR2
• The Biggest Splash
• The Milky Way's Stellar Disk
• APOGEE Chemical Abundance Patterns of the Massive Milky Way Satellites
• Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities
• Overview of the DESI Milky Way Survey
• MMT Hypervelocity Star Survey III: A Complete Survey of Faint B-type Stars in the Northern Milky Way Halo
• The chemical characterisation of halo substructure in the Milky Way based on APOGEE
• The Great Escape: Discovery of a nearby 1700 km/s star ejected from the Milky Way by Sgr A*
• The radial profile and flattening of the Milky Way's stellar halo to $80$kpc from the SEGUE K-giant Survey
• An Alternative Origin for Hypervelocity Stars
• Three-body encounters in the Galactic centre: the origin of the hypervelocity star SDSS J090745.0+024507
• Selecting accreted populations: metallicity, elemental abundances, and ages of the Gaia-Sausage-Enceladus and Sequoia populations
• The Milky Way's nuclear star cluster: Old, metal-rich, and cuspy
• Hyper Velocity Stars and the Restricted Parabolic 3-body Problem
• Discovery of low-metallicity stars in the central parsec of the Milky Way
• Hypervelocity Stars II. The Bound Population
• Galactic Archaeology with Gaia
• Gaia and the Galactic Center Origin of Hypervelocity Stars
• Production of Hypervelocity Stars through Encounters with Stellar-Mass Black Holes in the Galactic Centre
• Ejection of high-velocity stars from the Galactic Center by an inspiraling Intermediate-Mass Black Hole
• S-stars in the Galactic center and hypervelocity stars in the Galactic halo: two faces of the tidal breakup of stellar binaries by the central massive black hole?
• The Velocity Distribution of Hypervelocity Stars
• The inner two degrees of the Milky Way. Evidence of a chemical difference between the Galactic Center and the surrounding inner bulge stellar populations
• Binary Disruption by Massive Black Holes: Hypervelocity Stars, S Stars, and Tidal Disruption Events
• Ejection and Capture Dynamics in Restricted Three-Body Encounters
• Testing kinematic distances under a realistic Galactic potential
• Gaia DR3 in 6D: The search for fast hypervelocity stars and constraints on the Galactic Centre environment
• DESI Early Data Release Milky Way Survey Value-Added Catalogue
• Mapping the anisotropic Galactic stellar halo with Blue Horizontal Branch stars
• On measuring the Galactic dark matter halo with hypervelocity stars
• Impact of the Galactic Disk and Large Magellanic Cloud on the Trajectories of Hypervelocity Stars Ejected from the Galactic Center
• Constraints on the Galactic Centre environment from Gaia hypervelocity stars
• Constraints on the Galactic Centre environment from \textit{Gaia} hypervelocity stars III: Insights on a possible companion to Sgr A*
• Constraints on the Galactic Centre environment from Gaia hypervelocity stars II: The evolved population
• Probing the shape of the Milky Way dark matter halo with hypervelocity stars: a new method
• Dynamical mass distribution and velocity structure of the Galactic centre
• Double progenitor origin of the S-star cluster

Cited by in corpus (1)

• Discovery of Galactic center ejected star in DESI DR1