Cosmic-Ray Electrons in Groups and Clusters of Galaxies: Primary and Secondary Populations from a Numerical Cosmological Simulation

By Francesco Miniati, T. Jones, Hyesung Kang, Dongsu Ryu Max-Planck-Institut fuer Astrophysik, U. Minnesota, Pusan National University, Chungnam National University. 2001

198 citations recorded by the source corpus.

We investigate the generation and distribution of high-energy electrons in the cosmic structure environment and their observational consequences by carrying out the first cosmological simulation that includes directly cosmic-ray (CR) particles. Starting from cosmological initial conditions, in addition to the gas and dark matter related quantities, we follow the evolution of CR electrons (primary and secondary) and CR ions along with a passive magnetic field. CR ions and primary electrons are injected in accordance with the thermal leakage model and accelerated in the test-particle limit of diffusive shock acceleration at shocks associated with large-scale structure formation. Secondary electrons are continuously generated through p-p inelastic collisions of the CR ions with the thermal nuclei of the intergalactic medium. The evolution of the CR electrons accounts for spatial transport, adiabatic expansion/compression, and losses due to Coulomb collisions, bremsstrahlung, synchrotron and inverse-Compton emission. The magnetic field is seeded at shocks according to the Biermann battery model, and thereafter amplified by shear flow and gas compression. We compute the emission due to the inverse-Compton scattering of the simulated primary and secondary electrons off cosmic microwave background photons and compare it with the published values of the detected radiation excesses in the hard X-ray and extreme-ultraviolet wavebands. We find that the few instances of detection of hard X-ray radiation excess could be explained in the framework of IC emission from primary electrons in clusters characterized by high accretion/merger activity. On the other hand, with the only exception of measured flux from the Coma Cluster by Bowyer, Berghoefer & Korpela, both primary and secondary CR electrons associated with the cosmic structure formation account at most for a small fraction of the radiation excess detected in the extreme-ultraviolet waveband. Next, we calculate the synchrotron emission after normalizing the magnetic field strength so that for a Coma-like cluster the volume-averaged ⟨B2⟩1/2 ≃ 3 μG. Our results indicate that the synchrotron emission from the secondary CR electrons reproduces several general properties observed in radio halos. These include the recently found P1.4 GHz versus TX relationship, the morphology and polarization of the emitting region, and, to some extent, even the spectral index. In addition, radio synchrotron emission from primary electrons turns out to be large enough to power extended regions of radio emission, resembling radio relics observed at the outskirts of clusters. Once again we find a striking resemblance between the general properties of morphology, polarization, and spectral index of our synthetic maps and those of reported in the literature.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1a925a130c0da1edd2b49c189380503608ebf21c

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Citations in the corpus

Shock waves in Eulerian cosmological simulations: main properties and acceleration of cosmic rays (2008, methodology): “These shocks are commonly defined as ‘external shocks’ (Miniati et al. 2001), and they are the strongest within the simulation, having M 10.”
Cosmological Shocks in Adaptive Mesh Refinement Simulations and the Acceleration of Cosmic Rays (2008, background): “Cosmic rays from these low Mach number shocks will, however, have a steep energy spectrum and dissipate their energy relatively quickly compared to strong accretion shocks (e.g. Miniati et al. 2001).”
Alfvénic reacceleration of relativistic particles in galaxy clusters: MHD waves, leptons and hadrons (2003, background): “…radio emission (e.g. Roettiger, Burns & Stone 1999; Sarazin 1999; Takizawa & Naito 2000), however, the radiative lifetime of the emitting electrons diffusing away from these shocks is so short that they would just be able to produce relics and not Mpc-scale radio haloes (e.g. Miniati et al. 2001).”
Detecting shock waves in cosmological smoothed particle hydrodynamics simulations (2006, background): “Cosmological simulations support the possibility of a hadronic origin ofcluster radio haloes (Miniati et al. 2001).”
Radio signature of cosmological structure formation shocks (2006, background): “…origin of radio relics: They could either be caused by diffusive shock acceleration of electrons at the shock waves themselves (Enßlin et al. 1998; Miniati et al. 2001), or they could be old radio bubbles that are compressed by the passing shock wave and thus induced to emit observable…”
Constraining the population of cosmic ray protons in cooling flow clusters with γ-ray and radio observations: Are radio mini-halos of hadronic origin? (2003, background): “An increase ofXCRp(r) towards the cluster’s periphery is indeed observed in cosmological structure formation simulations due to adiabatic compression inside the cluster which increases the thermal pressure at a higher rate than the CRp pressure (Miniati et al. 2001a,b).”
Diffuse Radio Emission from Galaxy Clusters (2019, background): “Owing to their high-Mach numbers (M & 10), WHIM accretion shocks should accelerate particles (Miniati et al. 2001b; Ryu et al. 2003; Keshet et al. 2003), similar to what happens in clusters.”
Cosmic ray transport in galaxy clusters: implications for radio halos, gamma-ray signatures, and cool core heating (2010, background): “About two thirds of the most X-ray luminous clusters do not exhibit radio halos, whereas the hadronic model seems to suggests that all clusters exhibit halos (Miniati et al. 2001a; Miniati 2003; Pfrommer 2008; Pinzke & Pfrommer 2010).”
Simulating cosmic rays in clusters of galaxies – II. A unified scheme for radio haloes and relics with predictions of the γ-ray emission (2007, methodology): “There have been pioneering efforts to simulate the non-thermal emission from clusters by numerically modelling discretised cosmic ray (CR) energy spectra on top of Eulerian grid-based cosmological simulations (Miniati 2001; Miniati et al. 2001a,b; Miniati 2002, 2003).”
Cluster magnetic fields from galactic outflows (2008, background): “Models based on shock-induced field generation predict magnetic field strengths with a very weak dependence on the distance to the cluster centre and also predict a scaling of the mean magnetic field B ∝ √T (Miniati et al. 2001).”
DIFFUSIVE SHOCK ACCELERATION SIMULATIONS OF RADIO RELICS (2012, background): “In fact, with occasional pairings found in the opposite side of clusters and elongated morphologies, radio relics are commonly thought to reveal shock waves in intracluster media (ICMs) produced during mergers (e.g., Enßlin et al. 1998; Roettiger, Burns & Stone 1999; Miniati et al. 2001).”
Turbulent Motions and Shocks Waves in Galaxy Clusters simulated with AMR (2009, background): “Shocks in large scale structures have been investigated in a number of semi-analytical (Gabici & Blasi 2003; Berrington& Dermer 2003; Keshet et al.2003) and numerical works (Miniati et al.2001; Ryu et al 2003; Pfrommer et al.2007; Skillman et al.2008, Vazza et al.2008; Molnar et al.2009).”
Cosmological Shock Waves and Their Role in the Large-Scale Structure of the Universe (2003, background): “Short electron lifetimes, however, lead that population to depend on other factors (Miniati et al. 2001a).”
Gamma Rays from Intergalactic Shocks (2002, background): “Inverse Compton emission from shockaccelerated electrons in the hard X-ray (HXR) and extremeultraviolet (EUV) bands was recently studied by Miniati et al. (2001).”
SEARCH FOR COSMIC-RAY-INDUCED GAMMA-RAY EMISSION IN GALAXY CLUSTERS (2013, background): “…only a modest CR-to-thermal pressure ratio of (at most) a few percent (Dennison 1980; Vestrand 1982; Blasi & Colafrancesco 1999; Dolag & Enßlin 2000; Miniati et al. 2001a,b; Miniati 2003; Pfrommer & Enßlin 2003, 2004a,b; Blasi et al. 2007; Pfrommer et al. 2008; Pfrommer 2008; Kushnir et al. 2009;…”