A new type of compact stellar population: dark star clusters

Abstract

Among the most explored directions in the study of dense stellar systems is the investigation of the effects of the retention of supernova remnants, especially that of the massive stellar remnant black holes (BHs), in star clusters. By virtue of their eventual high central concentration, these stellar mass BHs potentially invoke a wide variety of physical phenomena, the most important ones being emission of gravitational waves (GWs), formation of X-ray binaries, and modification of the dynamical evolution of the cluster. Here we propose, for the first time, that rapid removal of stars from the outer parts of a cluster by the strong tidal field in the inner region of our Galaxy can unveil its BH sub-cluster, which appears as a star cluster that is gravitationally bound by an invisible mass. We study the formation and properties of such systems through direct N-body computations and estimate that they can be present in significant numbers in the inner region of the Milky Way. We call such objects "dark star clusters" (DSCs) as they appear dimmer than normal star clusters of similar mass and they comprise a predicted, new class of entities. The finding of DSCs will robustly cross-check BH retention; they will not only constrain the uncertain natal kicks of BHs, thereby the widely debated theoretical models of BH formation, but will also pinpoint star clusters as potential sites for GW emission for forthcoming ground-based detectors such as the Advanced LIGO. Finally, we also discuss the relevance of DSCs for the nature of IRS 13E.

14 pages, 4 figures. Published in The Astrophysical Journal Letters

References in corpus (11)

• Theory of Core-Collapse Supernovae
• An Extremely Top-Heavy IMF in the Galactic Center Stellar Disks
• Stellar-mass black holes in star clusters: implications for gravitational wave radiation
• Gemini and Hubble Space Telescope Evidence for an Intermediate Mass Black Hole in omega Centauri
• The mass function of young star clusters in spiral galaxies
• Black holes and core expansion in massive star clusters
• Compact Binaries in Star Clusters I - Black Hole Binaries Inside Globular Clusters
• Star Formation Around Super-Massive Black Holes
• Formation of black-hole X-ray binaries in globular clusters
• GC-IRS13E - A puzzling association of three early-type stars
• The X-ray Spectra of the Luminous LMXBs in NGC 3379: Field and Globular Cluster Sources

Cited by in corpus (37)

• MOCCA Code for Star Cluster Simulations - IV. A new Scenario for Intermediate Mass Black Hole Formation in Globular Clusters
• Dynamical evolution of black hole sub-systems in idealised star clusters
• Origin and growth of nuclear star clusters around massive black holes
• Stellar-mass black holes in young massive and open stellar clusters and their role in gravitational-wave generation II
• MOCCA-SURVEY Database I: Galactic Globular Clusters Harbouring a Black Hole Subsystem
• Binary Black Holes in Dense Star Clusters: Exploring the Theoretical Uncertainties
• On the distribution of stellar remnants around massive black holes: slow mass segregation, star cluster inspirals and correlated orbits
• A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5
• MOCCA Survey Database I: Dissolution of tidally filling star clusters harbouring BH subsystems
• Asymmetrical tidal tails of open star clusters: stars crossing their cluster's prah challenge Newtonian gravitation
• Black Hole Mergers from Star Clusters with Top-Heavy Initial Mass Functions
• Observational Evidence for a Dark Side to NGC5128's Globular Cluster System
• Gravitational wave of intermediate-mass black holes in Population III star clusters
• The mass-loss rates of star clusters with stellar-mass black holes: implications for the globular cluster mass function
• Growing Black Holes through Successive Mergers in Galactic Nuclei: I. Methods and First Results
• The Fifth Candidate for an Intermediate-mass Black Hole in the Galactic Center
• Chaos in self-gravitating many-body systems: Lyapunov time dependence of $N$ and the influence of general relativity
• A Possible Solution for the M/L-[Fe/H] Relation of Globular Clusters in M31: A metallicity and density dependent top-heavy IMF
• The Puzzling Negative Orbit-Period Derivative of the Low-Mass X-Ray Binary 4U 1820-30 in NGC 6624
• MOCCA-SURVEY Database I: Is NGC 6535 a Dark Star Cluster Harboring an IMBH?
• Searching in the dark: the dark mass content of the Milky Way globular clusters NGC288 and NGC6218
• Relativistic mergers of compact binaries in clusters: The fingerprint of the spin
• Impact of initial mass functions on the dynamical channel of gravitational wave sources
• Colliding Winds in and around the Stellar Group IRS 13E at the Galactic Center
• Finding Black Holes with Black Boxes -- Using Machine Learning to Identify Globular Clusters with Black Hole Subsystems
• The Lifetimes of Star Clusters Born with a Top-heavy IMF
• Supermassive black hole formation via collisions in black hole clusters
• Multiple stellar population mass loss in massive Galactic globular clusters
• The giants that were born swiftly -- Implications of the top-heavy stellar initial mass function on the birth conditions of globular clusters
• Binary black hole mergers from Population III star clusters
• The formation of globular clusters with top-heavy initial mass functions
• The Lost Dwarfs of Centaurus A and the Formation of its Dark Globular Clusters
• Dark Star Clusters or Ultra-Faint Dwarf galaxies? Revisiting UMa3/U1
• Compact stellar systems hosting an intermediate mass black hole: magnetohydrodynamic study of inflow-outflow dynamics
• Origin of High Dark Remnant Fractions in Milky Way Globular Clusters: The Crucial Role of Initial Black Hole Retention
• Gravitational wave inference of star cluster properties from intermediate-mass black hole mergers
• MOCCA-SURVEY Database I: Dissolution of tidally filling star clusters harboring black hole subsystem