Prospects and requirements for measurements of extragalactic γ-ray lines

Griffiths, R. E.

doi:10.1007/s10686-006-9053-2

Cited by 1 publication

(1 citation statement)

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“…It has recently been proposed that extended radio features of radio galaxies (Sambruna et al 2007; in case of Fornax A) and the interaction of CRs from AGN cavities with the ICM (Hinton, Domainko & Pope 2007; Hydra A) could be detectable with the Gamma‐ray Large Area Space Telescope. Moreover, it has been pointed out that the interaction of such CRs with the ICM could lead to significant annihilation line emission (Furlanetto & Loeb 2002; Griffiths 2005). We point out that our simulations add more weight to this idea and that a preferential diffusion of CRs in the wakes of rising bubbles could potentially lead to observable γ‐ray signatures.…”

Section: Astrophysical Consequencesmentioning

confidence: 99%

Cosmic ray confinement in fossil cluster bubbles

Ruszkowski

Enßlin

Brüggen

et al. 2007

Monthly Notices of the Royal Astronomical Society

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Most cool core clusters of galaxies possess active galactic nuclei (AGN) in their centers. These AGN inflate buoyant bubbles containing non-thermal radio emitting particles. If such bubbles efficiently confine cosmic rays (CR) then this could explain ``radio ghosts'' seen far from cluster centers. We simulate the diffusion of cosmic rays from buoyant bubbles inflated by AGN. Our simulations include the effects of the anisotropic particle diffusion introduced by magnetic fields. Our models are consistent with the X-ray morphology of AGN bubbles, with disruption being suppressed by the magnetic draping effect. We conclude that for such magnetic field topologies, a substantial fraction of cosmic rays can be confined inside the bubbles on buoyant rise timescales even when the parallel diffusivity coefficient is very large. For isotropic diffusion at a comparable level, cosmic rays would leak out of the bubbles too rapidly to be consistent with radio observations. Thus, the long confinement times associated with the magnetic suppression of CR diffusion can explain the presence of radio ghosts. We show that the partial escape of cosmic rays is mostly confined to the wake of the rising bubbles, and speculate that this effect could: (1) account for the excitation of the H$\alpha$ filaments trailing behind the bubbles in the Perseus cluster, (2) inject entropy into the metal enriched material being lifted by the bubbles and, thus, help to displace it permanently from the cluster center and (3) produce observable $\gamma$-rays via the interaction of the diffusing cosmic rays with the thermal intracluster medium (ICM).Comment: submitte

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Section: Astrophysical Consequencesmentioning

confidence: 99%