Disrupted globular clusters and the gamma-ray excess in the Galactic Centre

Giacomo Fragione; Fabio Antonini; Oleg Y. Gnedin

doi:10.1093/MNRAS/STY183

Disrupted globular clusters and the gamma-ray excess in the Galactic Centre

Giacomo Fragione^*, Fabio Antonini, Oleg Y. Gnedin

^*Corresponding author for this work

CIERA - Center for Interdisciplinary Exploration and Research in Astrophysics

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

Abstract

The Fermi Large Area Telescope has provided the most detailed view towards the Galactic Centre (GC) in high-energy gamma-rays. Besides the interstellar emission and point source contributions, the data suggest a residual diffuse gamma-ray excess. The similarity of its spatial distribution with the expected profile of dark matter has led to claims that this may be evidence for dark matter particle annihilation. Here, we investigate an alternative explanation that the signal originates from millisecond pulsars (MSPs) formed in dense globular clusters and deposited at the GC as a consequence of cluster inspiral and tidal disruption. We use a semi-analytical model to calculate the formation, migration, and disruption of globular clusters in the Galaxy. Our model reproduces the mass of the nuclear star cluster and the present-day radial and mass distribution of globular clusters. For the first time, we calculate the evolution of MSPs from disrupted globular clusters throughout the age of the Galaxy and consistently include the effect of theMSP spin-down due to magnetic-dipole braking. The final gamma-ray amplitude and spatial distribution are in good agreement with the Fermi observations and provide a natural astrophysical explanation for the GC excess.

Original language	English (US)
Pages (from-to)	5313-5321
Number of pages	9
Journal	Monthly Notices of the Royal Astronomical Society
Volume	475
Issue number	4
DOIs	https://doi.org/10.1093/MNRAS/STY183
State	Published - Apr 21 2018

Funding

We acknowledge Timothy Brandt, Tim Linden, Re’em Sari, Roberto Capuzzo-Dolcetta, and Manuel Arca-Sedda for useful discussions, and anonymous referee for constructive comments. GF acknowledges Moharana Reetanjali for useful discussions about the observed gamma-ray excess in the Galactic Centre and the modelling of MSP emission. FA acknowledges support by a CIERA postdoctoral fellowship at Northwestern University and the NASA Fermi Grant NNX15AU69G under which this project was initiated. OG acknowledges support from NASA through grant NNX12AG44G and from NSF through grant 1412144.

Keywords

Galaxies: star clusters: general
Galaxy: centre
Galaxy: kinematics and dynamics
Gamma-rays: diffuse background
Gamma-rays: galaxies
Pulsars: general

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1093/MNRAS/STY183

Cite this

@article{d4b452f63a8d4a72b96e204391a520b8,

title = "Disrupted globular clusters and the gamma-ray excess in the Galactic Centre",

abstract = "The Fermi Large Area Telescope has provided the most detailed view towards the Galactic Centre (GC) in high-energy gamma-rays. Besides the interstellar emission and point source contributions, the data suggest a residual diffuse gamma-ray excess. The similarity of its spatial distribution with the expected profile of dark matter has led to claims that this may be evidence for dark matter particle annihilation. Here, we investigate an alternative explanation that the signal originates from millisecond pulsars (MSPs) formed in dense globular clusters and deposited at the GC as a consequence of cluster inspiral and tidal disruption. We use a semi-analytical model to calculate the formation, migration, and disruption of globular clusters in the Galaxy. Our model reproduces the mass of the nuclear star cluster and the present-day radial and mass distribution of globular clusters. For the first time, we calculate the evolution of MSPs from disrupted globular clusters throughout the age of the Galaxy and consistently include the effect of theMSP spin-down due to magnetic-dipole braking. The final gamma-ray amplitude and spatial distribution are in good agreement with the Fermi observations and provide a natural astrophysical explanation for the GC excess.",

keywords = "Galaxies: star clusters: general, Galaxy: centre, Galaxy: kinematics and dynamics, Gamma-rays: diffuse background, Gamma-rays: galaxies, Pulsars: general",

author = "Giacomo Fragione and Fabio Antonini and Gnedin, {Oleg Y.}",

note = "Funding Information: We acknowledge Timothy Brandt, Tim Linden, Re{\textquoteright}em Sari, Roberto Capuzzo-Dolcetta, and Manuel Arca-Sedda for useful discussions, and anonymous referee for constructive comments. GF acknowledges Moharana Reetanjali for useful discussions about the observed gamma-ray excess in the Galactic Centre and the modelling of MSP emission. FA acknowledges support by a CIERA postdoctoral fellowship at Northwestern University and the NASA Fermi Grant NNX15AU69G under which this project was initiated. OG acknowledges support from NASA through grant NNX12AG44G and from NSF through grant 1412144. Publisher Copyright: {\textcopyright} 2017 The Authors.",

year = "2018",

month = apr,

day = "21",

doi = "10.1093/MNRAS/STY183",

language = "English (US)",

volume = "475",

pages = "5313--5321",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "4",

}

TY - JOUR

T1 - Disrupted globular clusters and the gamma-ray excess in the Galactic Centre

AU - Fragione, Giacomo

AU - Antonini, Fabio

AU - Gnedin, Oleg Y.

N1 - Funding Information: We acknowledge Timothy Brandt, Tim Linden, Re’em Sari, Roberto Capuzzo-Dolcetta, and Manuel Arca-Sedda for useful discussions, and anonymous referee for constructive comments. GF acknowledges Moharana Reetanjali for useful discussions about the observed gamma-ray excess in the Galactic Centre and the modelling of MSP emission. FA acknowledges support by a CIERA postdoctoral fellowship at Northwestern University and the NASA Fermi Grant NNX15AU69G under which this project was initiated. OG acknowledges support from NASA through grant NNX12AG44G and from NSF through grant 1412144. Publisher Copyright: © 2017 The Authors.

PY - 2018/4/21

Y1 - 2018/4/21

N2 - The Fermi Large Area Telescope has provided the most detailed view towards the Galactic Centre (GC) in high-energy gamma-rays. Besides the interstellar emission and point source contributions, the data suggest a residual diffuse gamma-ray excess. The similarity of its spatial distribution with the expected profile of dark matter has led to claims that this may be evidence for dark matter particle annihilation. Here, we investigate an alternative explanation that the signal originates from millisecond pulsars (MSPs) formed in dense globular clusters and deposited at the GC as a consequence of cluster inspiral and tidal disruption. We use a semi-analytical model to calculate the formation, migration, and disruption of globular clusters in the Galaxy. Our model reproduces the mass of the nuclear star cluster and the present-day radial and mass distribution of globular clusters. For the first time, we calculate the evolution of MSPs from disrupted globular clusters throughout the age of the Galaxy and consistently include the effect of theMSP spin-down due to magnetic-dipole braking. The final gamma-ray amplitude and spatial distribution are in good agreement with the Fermi observations and provide a natural astrophysical explanation for the GC excess.

AB - The Fermi Large Area Telescope has provided the most detailed view towards the Galactic Centre (GC) in high-energy gamma-rays. Besides the interstellar emission and point source contributions, the data suggest a residual diffuse gamma-ray excess. The similarity of its spatial distribution with the expected profile of dark matter has led to claims that this may be evidence for dark matter particle annihilation. Here, we investigate an alternative explanation that the signal originates from millisecond pulsars (MSPs) formed in dense globular clusters and deposited at the GC as a consequence of cluster inspiral and tidal disruption. We use a semi-analytical model to calculate the formation, migration, and disruption of globular clusters in the Galaxy. Our model reproduces the mass of the nuclear star cluster and the present-day radial and mass distribution of globular clusters. For the first time, we calculate the evolution of MSPs from disrupted globular clusters throughout the age of the Galaxy and consistently include the effect of theMSP spin-down due to magnetic-dipole braking. The final gamma-ray amplitude and spatial distribution are in good agreement with the Fermi observations and provide a natural astrophysical explanation for the GC excess.

KW - Galaxies: star clusters: general

KW - Galaxy: centre

KW - Galaxy: kinematics and dynamics

KW - Gamma-rays: diffuse background

KW - Gamma-rays: galaxies

KW - Pulsars: general

UR - http://www.scopus.com/inward/record.url?scp=85045585447&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85045585447&partnerID=8YFLogxK

U2 - 10.1093/MNRAS/STY183

DO - 10.1093/MNRAS/STY183

M3 - Article

AN - SCOPUS:85045585447

SN - 0035-8711

VL - 475

SP - 5313

EP - 5321

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 4

ER -

Disrupted globular clusters and the gamma-ray excess in the Galactic Centre

Abstract

Funding

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Cite this