17-22 July 2016
Master Cutlers Hall
Europe/London timezone

Discovery of a new extragalactic population of energetic particles

18 Jul 2016, 15:20
20m
Venue: Cutlers' Drawing Room (First Floor); Chair: Catherine De Clercq; Session Manager: Anthony Ezeribe ()

Venue: Cutlers' Drawing Room (First Floor); Chair: Catherine De Clercq; Session Manager: Anthony Ezeribe

Speaker

Mr. Thomas Lacroix (Institut d'Astrophysique de Paris)

Description

Radio galaxies are active galactic nuclei containing supermassive black holes with misaligned relativistic jets. Centaurus A (Cen A) is the closest known gamma-ray emitting radio galaxy. In this talk I will report the discovery of a hardening in the *Fermi*-LAT gamma-ray spectrum of the core of Cen A above 2.4 GeV, as well as evidence for variability below 2.4 GeV. These properties strongly support the hypothesis that the low energy component originates from leptons in the jet, while the additional source of very high energy particles near the core of Cen A must originate from a different cosmic-ray population. I will show that the observed gamma-ray spectrum is compatible with either a spike in the dark matter halo profile or a population of millisecond pulsars. This work constitutes the first robust indication of new gamma-ray production mechanisms in active galaxies and provides a tantalizing hint for the clustering of heavy dark matter particles around black holes.

Primary author

Mr. Thomas Lacroix (Institut d'Astrophysique de Paris)

Co-authors

Dr. Anthony Brown (Department of Physics and Centre for Advanced Instrumentation, Durham University) Dr. Céline Boehm (Institute for Particle Physics Phenomenology, Durham University) Mr. Jamie Graham (Department of Physics and Centre for Advanced Instrumentation, Durham University) Prof. Joseph Silk (Institut d'Astrophysique de Paris) Prof. Paula Chadwick (Department of Physics and Centre for Advanced Instrumentation, Durham University)

Presentation Materials

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