Dynamics of Intermediate-Mass Black Holes Wandering in the Milky Way Galaxy Using the Illustris TNG50 Simulation

Abstract

The detection of Intermediate-Mass Black Holes (IMBHs) in dwarf galaxies is crucial to closing the gap in the wide mass distribution of black holes ($\sim 3{\mathrm{M}}_{\odot }$ to $\sim 5\times 10^{10}{\mathrm{M}}_{\odot }$). IMBHs originally located at the center of dwarfs that later collide with the Milky Way (MW) could be wandering, undetected, in our Galaxy. We used TNG50, the highest-resolution run of the IllustrisTNG project, to study the kinematics and dynamics of star clusters, in the appropriate mass range, acting as IMBH proxies in a MW analog galaxy. We showed that $\sim 87\%$ of our studied IMBHs drift inward. The radial velocity of these sinking IMBHs has a median magnitude of $\sim 0.44\mathrm{ckpc}{\mathrm{h}}^{-1}\mathrm{Gy}{\mathrm{r}}^{-1}$ and no dependence on the black hole mass. The central $1\mathrm{ckpc}{\mathrm{h}}^{-1}$ has the highest number density of IMBHs in the galaxy. A physical toy model with linear drag forces was developed to explain the orbital circularization with time. These findings constrain the spatial distribution of IMBHs, suggesting that future searches should focus on the central regions of the Galaxy. Additionally, we found that the 3D velocity distribution of IMBHs with respect to the galactic center has a mean of $\sim 180\mathrm{km}{\mathrm{s}}^{-1}$ and larger variance with decreasing radius. Remarkably, the velocity distribution relative to the local gas shows significantly lower values, with a mean of $\sim 88\mathrm{km}{\mathrm{s}}^{-1}$. These results are instrumental for predicting the accretion and radiation properties of IMBHs, facilitating their detection with future surveys.

Accepted for publication in MNRAS. This is the final version of the manuscript. 10 pages, 12 figures

References in corpus (19)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• Laser Interferometer Space Antenna
• Advection-Dominated Accretion and the Black Hole Event Horizon
• A Luminous Quasar at Redshift 7.642
• Rapid Formation of Supermassive Black Hole Binaries in Galaxy Mergers with Gas
• Rapid growth of seed black holes in the early universe by supra-exponential accretion
• Improved Dynamical Constraints on the Masses of the Central Black Holes in Nearby Low-mass Early-type Galactic Nuclei And the First Black Hole Determination for NGC 205
• The velocity dispersion and mass profile of the Milky Way
• The erratic dynamical life of black hole seeds in high-redshift galaxies
• Wandering Black Holes in Bright Disk Galaxy Halos
• Intermediate-mass Black Holes from High Massive-star Binary Fractions in Young Star Clusters
• Origins and Demographics of Wandering Black Holes
• Populating the low-mass end of the $M_{\mathrm{BH}}-{\sigma }_{\ast }$ relation
• Separating Accretion and Mergers in the Cosmic Growth of Black Holes with X-ray and Gravitational Wave Observations
• Unveiling the Population of Wandering Black Holes via Electromagnetic Signatures
• The Active Fraction of Massive Black Holes in Dwarf Galaxies
• Hubble Space Telescope Imaging of the Active Dwarf Galaxy RGG 118
• Ultramassive black holes in the most massive galaxies: $M_{\mathrm{BH}}-\sigma$ versus $M_{\mathrm{BH}}-R_{\mathrm{b}}$
• Modelling mass distribution of the Milky Way galaxy using Gaia billion-star map

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