Dynamical formation of Gaia BH3 in the progenitor globular cluster of the ED-2 stream

Abstract

Context. The star-black hole (S-BH) binary known as Gaia BH3, discovered by the Gaia Collaboration is chemically and kinematically associated with the metal-poor ED-2 stream in the Milky Way halo. Aims. We explore the possibility that Gaia BH3 was assembled dynamically in the progenitor globular cluster (GC) of the ED-2 stream. Methods. We used a public suite of star-by-star dynamical Monte Carlo models to identify S-BH binaries in GCs with different initial masses and (half-mass) radii. Results. We show that a likely progenitor of the ED-2 stream was a relatively low-mass ($\lesssim 10^5{M}_{\odot }$) GC with an initial half-mass radius of ~4 pc. Such a GC can dynamically retain a large fraction of its BH population and dissolve on the orbit of ED-2. From the suite of models we find that GCs produce ~ 3 - 30 S-BH binaries, approximately independent of initial GC mass and inversely correlated with initial cluster radius. Scaling the results to the Milky Way GC population, we find that ~75% of the S-BH binaries formed in GCs are ejected from their host GC, all in the early phases of evolution ($\lesssim 1$ Gyr); these are expected to no longer be close to streams. The ~25% of S-BH binaries retained until dissolution are expected to form part of streams, such that for an initial mass of the progenitor of ED-2 of a few $10^4{M}_{\odot }$, we expect ~2-3 S-BH to end up in the stream. GC models with metallicities similar to Gaia BH3 ($\lesssim 1\%$ solar) include S-BH binaries with similar BH masses ($\gtrsim 30M_{\odot }$), orbital periods, and eccentricities. Conclusions. We predict the Galactic halo contains of order $10^5$ S-BH binaries that formed dynamically in GCs, a fraction of which may readily be detected in Gaia DR4. The detection of these sources provides valuable tests of BH dynamics in clusters and the possible role in formation of gravitational wave sources.

5 pages, 3 figures, accepted in A&A

References in corpus (22)

• X-ray Properties of Black-Hole Binaries
• MOCCA-SURVEY Database I: Coalescing Binary Black Holes Originating From Globular Clusters
• Illuminating Black Hole Binary Formation Channels with Spins in Advanced LIGO
• The ACS Virgo Cluster Survey. XII. The Luminosity Function of Globular Clusters in Early Type Galaxies
• A Sun-like star orbiting a black hole
• A red giant orbiting a black hole
• Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry
• Modeling Dense Star Clusters in the Milky Way and Beyond with the Cluster Monte Carlo Code
• Intermediate-mass Black Holes from High Massive-star Binary Fractions in Young Star Clusters
• The Gaia DR3 view of dynamical substructure in the stellar halo near the Sun
• Apples and Oranges: Comparing black holes in X-ray binaries and gravitational-wave sources
• Coalescing black hole binaries from globular clusters: mass distributions and comparison to gravitational wave data from GWTC-3
• A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5
• Accreting black hole binaries in globular clusters
• Evidence for a bottom-light initial mass function in massive star clusters
• Black Hole Mergers from Star Clusters with Top-Heavy Initial Mass Functions
• Stellar Escape from Globular Clusters. I. Escape Mechanisms and Properties at Ejection
• The mass-loss rates of star clusters with stellar-mass black holes: implications for the globular cluster mass function
• The 33 M${}_{\odot }$ black hole Gaia BH3 is part of the disrupted ED-2 star cluster
• Multimass modelling of Milky Way globular clusters -- I. Implications on their stellar initial mass function above 1 M${}_{\odot }$
• ED-2: a cold but not so narrow stellar stream crossing the Solar neighbourhood
• Compact Binary Formation in Open Star Clusters II: Difficulty of Gaia NS formation in low-mass star clusters

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