A Population of Relic Intermediate-Mass Black Holes in the Halo of the Milky Way

Abstract

If "seed" central black holes were common in the subgalactic building blocks that merged to form present-day massive galaxies, then relic intermediate-mass black holes (IMBHs) should be present in the Galactic bulge and halo. We use a particle tagging technique to dynamically populate the N-body Via Lactea II high-resolution simulation with black holes, and assess the size, properties, and detectability of the leftover population. The method assigns a black hole to the most tightly bound central particle of each subhalo at infall according to an extrapolation of the M_BH-sigma_* relation, and self-consistently follows the accretion and disruption of Milky Way progenitor dwarfs and their holes in a cosmological "live" host from high redshift to today. We show that, depending on the minimum stellar velocity dispersion, sigma_m, below which central black holes are assumed to be increasingly rare, as many as ~2000 (sigma_m=3 km/s) or as few as ~70 (sigma_m=12 km/s) IMBHs may be left wandering in the halo of the Milky Way today. The fraction of IMBHs kicked out of their host by gravitational recoil is < 20%. We identify two main Galactic subpopulations, "naked" IMBHs, whose host subhalos were totally destroyed after infall, and "clothed" IMBHs residing in dark matter satellites that survived tidal stripping. Naked IMBHs typically constitute 40-50% of the total and are more centrally concentrated. We show that, in the sigma_m=12 km/s scenario, the clusters of tightly bound stars that should accompany naked IMBHs would be fainter than m_V=16 mag, spatially resolvable, and have proper motions of 0.1-10 milliarcsec per year. Their detection may provide an observational tool to constrain the formation history of massive black holes in the early Universe.

9 pages, 8 figures, minor changes to match version accepted by the Astrophysical Journal

References in corpus (12)

• Revisiting the Scaling Relations of Black Hole Masses and Host Galaxy Properties
• Formation of Supermassive Black Holes by Direct Collapse in Pregalactic Halos
• Dwarf Galaxies with Optical Signatures of Active Massive Black Holes
• Direct cosmological simulations of the growth of black holes and galaxies
• Supermassive black hole formation during the assembly of pre-galactic discs
• A 15.65 solar mass black hole in an eclipsing binary in the nearby spiral galaxy Messier 33
• Constraining the Statistics of Population III Binaries
• Early supersymmetric cold dark matter substructure
• The M31 Velocity Vector. I. Hubble Space Telescope Proper Motion Measurements
• Limits on intermediate-mass black holes in six Galactic globular clusters with integral-field spectroscopy
• Star Clusters Around Recoiled Black Holes in the Milky Way Halo
• Direct Gravitational Imaging of Intermediate Mass Black Holes in Extragalactic Halos

Cited by in corpus (33)

• Intermediate-Mass Black Holes
• Primordial Black Holes as Generators of Cosmic Structures
• Initial mass function of intermediate mass black hole seeds
• Gravitational waves as a probe of dark matter mini-spikes
• Feedback by Massive Black Holes in Dwarf Galaxies
• Illuminating Massive Black Holes With White Dwarfs: Orbital Dynamics and High Energy Transients from Tidal Interactions
• Origins and Demographics of Wandering Black Holes
• Understanding black hole mass assembly via accretion and mergers at late times in cosmological simulations
• The Formation of Intermediate Mass Black Holes in Galactic Nuclei
• Lessons from the curious case of the `fastest' star in Gaia DR2
• A Unique Multi-Messenger Signal of QCD Axion Dark Matter
• The impact of reionization on the formation of supermassive black hole seeds
• Effect of Black Holes in Local Dwarf Spheroidal Galaxies on Gamma-Ray Constraints on Dark Matter Annihilation
• Intermediate Mass-Ratio Inspirals with Dark Matter Minispikes
• Where intermediate-mass black holes could hide in the Galactic Centre: A full parameter study with the S2 orbit
• Ultrahigh-energy cosmic rays from tidally-ignited white dwarfs
• Formation of Dark Matter Torii Around Supermassive Black Holes Via The Eccentric Kozai-Lidov Mechanism
• A Stability Timescale for Non-Hierarchical Three-Body Systems
• Constraining a companion of the galactic center black hole, Sgr A*
• The imprint of the cosmic supermassive black hole growth history on the 21 cm background radiation
• Subhalo sinking and off-center massive black holes in dwarf galaxies
• Monochromatic neutrino lines from sneutrino dark matter
• Intermediate mass black holes and dark matter at the Galactic center
• Gravitational waves from an SMBH binary in M87
• Gravitational lensing of gravitational waves: prospects for probing intermediate-mass black holes in galaxy lenses with global minima image
• Off-centre supermassive black holes in bright central galaxies
• An Unusual Transient in the Extremely Metal-Poor Galaxy SDSS J094332.35+332657.6 (Leoncino Dwarf)
• Hypercompact stellar clusters: morphological renditions and spectro-photometric models
• Constraining the population of intermediate mass black holes by gamma-ray data of the Fornax cluster
• Discovery of faint double-peak Halpha emission in the halo of low redshift galaxies
• Detecting floating black holes as they traverse the gas disk of the Milky Way
• A Search for Wandering Black Holes in the Milky Way with Gaia and DECaLS
• Gravitational signatures beyond Newton: exploring hierarchical three-body dynamics