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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 731836.0, MPI für Astronomie / Publikationen_mpia
Evidence of Fermi bubbles around M31
Authors:Pshirkov, M. S.; Vasiliev, V. V.; Postnov, K. A.
Date of Publication (YYYY-MM-DD):2016
Title of Journal:Monthly Notices of the Royal Astronomical Society
Issue / Number:1
Start Page:L76
End Page:L80
Audience:Not Specified
Abstract / Description:Gamma-ray haloes can exist around galaxies due to the interaction of escaping galactic cosmic rays with the surrounding gas. We have searched for such a halo around the nearby giant spiral Andromeda galaxy M31 using almost 7 yr of Fermi LAT data at energies above 300 MeV. The presence of a diffuse gamma-ray halo with total photon flux 2.6 ± 0.6 × 10-9 cm-2 s-1, corresponding to a luminosity (0.3-100 GeV) of (3.2 ± 0.6) × 1038 erg s-1 (for a distance of 780 kpc) was found at a 5.3σ confidence level. The halo form does not correspond to the extended baryonic H I disc of M31, as would be expected in hadronic production of gamma photons from cosmic ray interaction, nor it is spherically symmetric, as could be in the case of dark matter annihilation. The best-fitting halo template corresponds to two 6-7.5 kpc bubbles symmetrically located perpendicular to the M31 galactic disc, similar to the `Fermi bubbles' found around the Milky Way centre, which suggests the past activity of the central supermassive black hole or a star formation burst in M31.
Free Keywords:cosmic rays; ISM: magnetic fields; galaxies: individual: M31; gamma rays: galaxies
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0035-8711 %R 10.1093/mnrasl/slw045
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