Millisecond Pulsars in Dense Star Clusters: Evolution, Scaling Relations, and the Galactic-Center Gamma-ray Excess

Abstract

The number of millisecond pulsars (MSPs) observed in Milky Way globular clusters has increased explosively in recent years, but the underlying population is still uncertain due to observational biases. We use state-of-the-art $N$-body simulations to study the evolution of MSP populations in dense star clusters. These cluster models span a wide range in initial conditions, including different initial masses, metallicities, and virial radii, which nearly cover the full range of properties exhibited by the population of globular clusters in the Milky Way. We demonstrate how different initial cluster properties affect the number of MSPs, for which we provide scaling relations as a function of cluster age and mass. As an application, we use our formulae to estimate the number of MSPs delivered to the Galactic Center from inspiralling globular clusters to probe the origin of the Galactic-Center gamma-ray excess detected by Fermi. We predict about $400$ MSPs in the Galactic Center from disrupted globular clusters, which can potentially explain most of the observed gamma-ray excess.

14 pages, 15 figures. Accepted for publication in ApJ

References in corpus (15)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Background model systematics for the Fermi GeV excess
• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• Formation and evolution of compact binaries in globular clusters: II. Binaries with neutron stars
• The Dynamical Evolution of Stellar Black Holes in Globular Clusters
• N-body modeling of globular clusters: Masses, mass-to-light ratios and intermediate-mass black holes
• Lifetimes of tidally limited star clusters with different radii
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• Eight new millisecond pulsars from the first MeerKAT globular cluster census
• Millisecond Pulsars and Black Holes in Globular Clusters
• FAST Globular Cluster Pulsar Survey: Twenty-Four Pulsars Discovered in Fifteen Globular Clusters
• The global mass functions of 35 Galactic globular clusters: I. Observational data and correlations with cluster parameters
• Populating the Galaxy with pulsars I: stellar & binary evolution
• The Gamma-Ray Pulsar Population of Globular Clusters: Implications for the GeV Excess
• Probing the formation history of the nuclear star cluster at the Galactic Centre with millisecond pulsars