Structure and Skewness of the Effective Inspiral Spin Distribution of Binary Black Hole Mergers

Abstract

The detection of gravitational waves has brought to light a population of binary black holes that merge within a Hubble time. Multiple formation channels can contribute to this population, making it difficult to definitively associate particular population features with underlying stellar physics. Black hole spins are considered an important discriminator between various channels, but they are less well-measured than masses, making conclusive astrophysical statements using spins difficult thus far. In this paper, we consider the distribution of the effective inspiral spin ${\chi }_{\mathrm{eff}}$ -- a quantity much better measured than individual component spins. We show that non-Gaussian features like skewness, asymmetry about zero, and multimodality can naturally arise in the ${\chi }_{\mathrm{eff}}$ distribution when multiple channels contribute to the population. Searching for such features, we find signs of skewness and asymmetry already in the current catalogs, but no statistically significant signs of bimodality. These features provide robust evidence for the presence of a subpopulation with spins preferentially aligned to the binary's orbital angular momentum; and we conservatively estimate the fraction of this subpopulation to be at least $12\%-17\%$ (at $90\%$ credibility). Our models do not find an excess of non-spinning systems and instead find that at least $\sim 20\%$ of the binaries have some degree of negative ${\chi }_{\mathrm{eff}}$. The data also suggest that, if preferentially aligned mergers form a significant fraction of the population, they must have small spins.

17 pages, 7 figures

References in corpus (34)

• Advanced Virgo: a 2nd generation interferometric gravitational wave detector
• Advanced LIGO
• GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo During the Second Part of the Third Observing Run
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• Properties and astrophysical implications of the 150 Msun binary black hole merger GW190521
• Towards models of gravitational waveforms from generic binaries II: Modelling precession effects with a single effective precession parameter
• Illuminating Black Hole Binary Formation Channels with Spins in Advanced LIGO
• Analysis of spin precession in binary black hole systems including quadrupole-monopole interaction
• One Channel to Rule Them All? Constraining the Origins of Binary Black Holes using Multiple Formation Pathways
• Merging black hole binaries: the effects of progenitor's metallicity, mass-loss rate and Eddington factor
• Lidov-Kozai Cycles with Gravitational Radiation: Merging Black Holes in Isolated Triple Systems
• Distinguishing Spin-Aligned and Isotropic Black Hole Populations With Gravitational Waves
• Hierarchical mergers of stellar-mass black holes and their gravitational-wave signatures
• POSYDON: A General-Purpose Population Synthesis Code with Detailed Binary-Evolution Simulations
• GW190521 as a dynamical capture of two nonspinning black holes
• General-relativistic precession in a black-hole binary
• Distribution of Effective Spins and Masses of Binary Black Holes from the LIGO and Virgo O1-O3a Observing Runs
• Cover Your Basis: Comprehensive Data-Driven Characterization of the Binary Black Hole Population
• Building better spin models for merging binary black holes: Evidence for non-spinning and rapidly spinning nearly aligned sub-populations
• Apples and Oranges: Comparing black holes in X-ray binaries and gravitational-wave sources
• A Parameter-Free Tour of the Binary Black Hole Population
• Resolving the Stellar-Collapse and Hierarchical-Merger origins of the Coalescing Black Holes
• The population properties of spinning black holes using Gravitational-wave Transient Catalog 3
• Do unequal-mass binary black hole systems have larger ${\chi }_{\text{eff}}$? Probing correlations with copulas in gravitational-wave astronomy
• LIGO--Virgo correlations between mass ratio and effective inspiral spin: testing the active galactic nuclei channel
• Quiescent and active galactic nuclei as factories of merging compact objects in the era of gravitational-wave astronomy
• Limits on hierarchical black hole mergers from the most negative ${\chi }_{\mathrm{eff}}$ systems
• Spin it as you like: the (lack of a) measurement of the spin tilt distribution with LIGO-Virgo-KAGRA binary black holes
• Symmetry Breaking in Dynamical Encounters in the Disks of Active Galactic Nuclei
• Evidence for a correlation between binary black hole mass ratio and black-hole spins
• Black-hole mergers in disklike environments could explain the observed $q$-${\chi }_{\mathrm{eff}}$ correlation
• GW190521: tracing imprints of spin-precession on the most massive black hole binary
• Dropping Anchor: Understanding the Populations of Binary Black Holes with Random and Aligned Spin Orientations
• Which black hole is spinning? Probing the origin of black-hole spin with gravitational waves

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