Gamma Rays from Intergalactic Shocks

By U. Keshet, E. Waxman, Abraham Loeb, Volker Springel, L. Hernquist. 2002

143 citations recorded by the source corpus.

Structure formation in the intergalactic medium (IGM) produces large-scale, collisionless shock waves, in which electrons can be accelerated to highly relativistic energies. Such electrons can Compton-scatter cosmic microwave background photons up to γ-ray energies. We study the radiation emitted in this process using a hydrodynamic cosmological simulation of a ΛCDM universe. The resulting radiation, extending beyond TeV energies, has roughly constant energy flux per decade in photon energy, in agreement with the predictions of Loeb & Waxman. Assuming that a fraction ξe = 0.05 of the shock thermal energy is transferred to the population of accelerated relativistic electrons, as inferred from collisionless nonrelativistic shocks in the interstellar medium, we find that the energy flux of this radiation, ϵ2(dJ/dϵ) ≃ 50-160 eV cm-2 s-1 sr-1, constitutes ~10% of the extragalactic γ-ray background flux. The associated γ-ray point sources are too faint to account for the ~60 unidentified EGRET γ-ray sources, but GLAST should detect and resolve several γ-ray sources associated with large-scale IGM structures for ξe ≃ 0.03 and many more sources for larger ξe. The intergalactic origin of the shock-induced radiation can be verified through a cross-correlation with, e.g., the galaxy distribution that traces the same structure. Its shock origin may be tested by cross-correlating its properties with radio synchrotron radiation, emitted as the same accelerated electrons gyrate in postshock magnetic fields. We predict that GLAST and Cerenkov telescopes such as MAGIC, VERITAS, and HESS should resolve γ-rays from nearby (redshifts z ≲ 0.01) rich galaxy clusters, perhaps in the form of a ~5-10 Mpc diameter ringlike emission tracing the cluster accretion shock, with luminous peaks where the ring intersects galaxy filaments detectable even at z ≃ 0.025.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/cfe27e237a88fe65d63b2c988b84ab744f13222f

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Citations in the corpus

THE FERMI-LAT HIGH-LATITUDE SURVEY: SOURCE COUNT DISTRIBUTIONS AND THE ORIGIN OF THE EXTRAGALACTIC DIFFUSE BACKGROUND (2010, background): “Intergalactic shocks produced by the assembly of Large Scale Structures (e.g. Loeb & Waxman 2000; Miniati 2002; Keshet et al. 2003; Gabici & Blasi 2003), γ -ray emission from galaxy clusters (e.g. Berrington & Dermer 2003; Pfrommer et al. 2008), emission from starburst as well as normal galaxies…”
CONTRIBUTION OF GAMMA-RAY-LOUD RADIO GALAXIES’ CORE EMISSIONS TO THE COSMIC MeV AND GeV GAMMA-RAY BACKGROUND RADIATION (2011, background): “These are intergalactic shocks produced by the large-scale structure formation (Loeb & Waxman 2000; Totani & Kitayama 2000; Miniati 2002; Keshet et al. 2003; Gabici & Blasi 2003), normal and starburst galaxies (Pavlidou & Fields 2002; Thompson et al. 2007; Bhattacharya & Sreekumar 2009; Makiya et…”
Radio signature of cosmological structure formation shocks (2006, methodology): “Typically, the maximum energy is estimated by comparing the acceleration e-folding time and the cooling time (Keshet et al. 2003).”
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.”
Magnetic Fields in Starburst Galaxies and the Origin of the FIR-Radio Correlation (2006, methodology): “This is similar to standard estimates for the fraction of SN energy supplied to relativistic electrons (see, e.g., x 2.2.2 of Keshet et al. 2003 for a summary), which supports the hypothesis that coolP esc.”
THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION (2009, background): “Similarly, large scale cosmological structure formation scenarios predict high-energyγ-ray emission from galaxy clusters at a level detectable forFermi/LAT (Keshet et al. 2003).”
Moving mesh cosmology: tracing cosmological gas accretion (2013, background): “It also gains the strengths of finite volume codes, including the improved treatment of fluid instabilities, weak shocks (which can be missed in SPH; (e.g. Keshet et al. 2003)), phase interfaces, and shearing flows.”
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).”
The Starburst Contribution to the Extragalactic γ-Ray Background (2006, background): “…1996), galaxy clusters and groups (Colafrancesco&Blasi 1998; Dar & Shaviv 1995), intergalactic shocks and structure formation (Loeb & Waxman 2000; Keshet et al. 2003; Miniati 2002), dark matter annihilation (e.g., Ullio et al. 2002; Elsässer & Mannheim 2005), and normal star-forming galaxies…”
Shock waves in Eulerian cosmological simulations: main properties and acceleration of cosmic rays (2008, methodology): “This subject has been already investigated in several papers under different numerical approaches (Miniati et al. 2000, 2001; Keshet et al. 2003; Ryu et al. 2003; Pfrommer et al. 2006; Kang et al. 2007; Pfrommer et al. 2007).6 We study shock waves by means of a post-processing procedure.”
Detecting shock waves in cosmological smoothed particle hydrodynamics simulations (2006, methodology): “Previous work on shock detection in SPH simulations (Keshet et al. 2003) was restricted to a posteriori analysis of two subsequent simulation time-slices, which can then be used to approximately detect a certain range of shocks as entropy jumps.”
Simulating cosmic rays in clusters of galaxies – II. A unified scheme for radio haloes and relics with predictions of the γ-ray emission (2007, background): “(A25) Keshet et al. (2003) suggest a value ofζmax ≃ 0.05 for the limiting case of the electron energy injection efficiency.”