Millisecond pulsars and the gamma-ray excess in Andromeda

Abstract

The Fermi Gamma-Ray Space Telescope has provided evidence for diffuse gamma-ray emission in the central parts of the Milky Way and the Andromeda galaxy. This excess has been interpreted either as dark matter annihilation emission or as emission from thousands of millisecond pulsars (MSPs). We have recently shown that old massive globular clusters may move towards the center of the Galaxy by dynamical friction and carry within them enough MSPs to account for the observed gamma-ray excess. In this paper we revisit the MSP scenario for the Andromeda galaxy, by modeling the formation and disruption of its globular cluster system. We find that our model predicts gamma-ray emission $\sim 2-3$ times larger than for the Milky Way, but still nearly an order of magnitude smaller than the observed Fermi excess in the Andromeda. Our MSP model can reproduce the observed excess only by assuming $\sim 8$ times larger number of old clusters than inferred from galaxy scaling relations. To explain the observations we require either that Andromeda deviates significantly from the scaling relations, or that a large part of its high-energy emission comes from additional sources.

5 pages, 2 figures, 1 Table, accepted by ApJ Lett

References in corpus (19)

• The Spectrum and Morphology of the Fermi Bubbles
• A Tale of Tails: Dark Matter Interpretations of the Fermi GeV Excess in Light of Background Model Systematics
• A fitting formula for the merger timescale of galaxies in hierarchical clustering
• The M31 Velocity Vector. II. Radial Orbit Towards the Milky Way and Implied Local Group Mass
• The life cycle of star cluster in a tidal field
• Lifetimes of tidally limited star clusters with different radii
• Galactic Dark Matter Halos and Globular Cluster Populations. III: Extension to Extreme Environments
• Orbits of Massive Satellite Galaxies: I. A Close Look at the Large Magellanic Cloud and a New Orbital History for M33
• Formation of Globular Cluster Systems: From Dwarf Galaxies to Giants
• Observations of M31 and M33 with the Fermi Large Area Telescope: a galactic center excess in Andromeda?
• An updated survey of globular clusters in M31. II Newly discovered bright and remote clusters
• Distinguishing Dark Matter from Unresolved Point Sources in the Inner Galaxy with Photon Statistics
• On the origins of enigmatic stellar populations in Local Group galactic nuclei
• Millisecond pulsar origin of the Galactic center excess and extended gamma-ray emission from Andromeda - a closer look
• Disrupted Globular Clusters and the Gamma-Ray Excess in the Galactic Centre
• Gamma-ray and X-ray emission from the Galactic Centre: hints on the nuclear star cluster formation history
• Neutron stars and millisecond pulsars in star clusters: implications for the diffuse $\gamma$-radiation from the Galactic Centre
• A Multi-Wavelength Analysis of Annihilating Dark Matter as the Origin of the Gamma-Ray Emission from M31
• The Star Formation History in the M31 Bulge

Cited by in corpus (12)

• Neutron stars and millisecond pulsars in star clusters: implications for the diffuse $\gamma$-radiation from the Galactic Centre
• Supermassive black holes coalescence mediated by massive perturbers: implications for gravitational waves emission and nuclear cluster formation
• Binary intermediate-mass black hole mergers in globular clusters
• Exploring A Cosmic-Ray Origin of the Multi-wavelength Emission in M31
• TeV Dark Matter Searches in the Extragalactic Gamma-Ray Sky
• Hunting intermediate-mass black holes with LISA binary radial velocity measurements
• Gamma-ray image reconstruction of the Andromeda galaxy
• The Andromeda Gamma-Ray Excess: Background Systematics of the Millisecond Pulsars and Dark Matter Interpretations
• On Dark Matter Explanations of the Gamma-Ray Excesses from the Galactic Center and M31
• Cosmic-ray transport and gamma-ray emission in M31
• Measuring the Mass of Missing Baryons in the Halo of Andromeda Galaxy with Gamma-Ray Observations
• On the Gamma-Ray Emission of the Andromeda Galaxy M31