Cosmic γ-ray background from structure formation in the intergalactic medium

By Abraham Loeb, E. Waxman. Nature, 2000

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The Universe is filled with a diffuse background of γ-ray radiation, the origin of which remains one of the unsolved puzzles of cosmology. Less than one-quarter of the γ-ray flux can be attributed to unresolved discrete sources, such as active galactic nuclei; the remainder appears to constitute a truly diffuse background. Here we show that the shock waves induced by gravity in the gas of the intergalactic medium, during the formation of large-scale structures like filaments and sheets of galaxies, produce a population of highly relativistic electrons. These electrons scatter a small fraction of the cosmic microwave background photons in the local Universe up to γ-ray energies, thereby providing the γ-ray background. The predicted diffuse flux agrees with the observed background across more than four orders of magnitude in photon energy, and the model predicts that the γ-ray background, though generated locally, is isotropic to better than five per cent on angular scales larger than a degree. Moreover, the agreement between the predicted and observed background fluxes implies a mean cosmological density of baryons that is consistent with Big Bang nucleosynthesis.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/70cdcbf7848c65ff16f9dbb3d0b35d1a86a873b0

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Citations in the corpus

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…”
A New Determination of the Extragalactic Diffuse Gamma-Ray Background from EGRET Data (2004, unknown): “Contributions from other extragalactic sources have been plausibly suggested: galaxy clusters (Ensslin et al. 1997), energetic particles in the shock waves associated with large scale cosmological structure formation (Loeb & Waxman 2000; Miniati 2002), or distant γ-ray burst events.”
The Starburst Contribution to the Extragalactic γ-Ray Background (2006, background): “…(Stecker & Salamon 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…”
Intergalactic Magnetic Fields from Quasar Outflows (2001, background): “The future GLAST mission1 will have the sensitivity and angular resolution necessary to map the predicted γray luminosity of galaxy clusters and correlate it with low-frequency radio maps of the same regions (Loeb & Waxman 2000; Waxman & Loeb 2000).”
THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION (2009, background): “…representatives of other extragalactic γ-ray sources, such as galaxy clusters (Dar & Shaviv 1995; Colafrancesco & Blasi 1998; Totani & Kitayama 2000; Loeb & Waxman 2000; Gabici & Blasi 2003), will enable comparisons and normalization of theoretical predictions of their contributions to the EGRB.”
The Cosmic Energy Inventory (2004, background): “Cosmic rays might gain energy from shocks produced by streaming motions of magnetized warm plasma in the vicinity of galaxies (Loeb & Waxman 2000).”
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…”
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): “It has been proposed that a fractionof the diffuse cosmologicalγ-ray background radiation originates from the same processes (Loeb & Waxman 2000; Miniati 2002; Reimer et al. 2003; Berrington & Dermer 2003; Kuo et al. 2005).”
Reionization by Hard Photons. I. X-Rays from the First Star Clusters (2000, background): “…Ostriker 1992), annihilation of weakly interactive big bang remnants (Silk & Srednicki 1984 ; Rudaz & Stecker 1991), and Ðnally, inverse Compton radiation from cosmic-ray electrons in our own Galaxy (Strong & Moskalenko 1998 ; Dar & De Rujula 2000) and from collapsing clusters (Loeb & Waxman 2000).”
THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND AND IMPLICATIONS FOR DARK MATTER ANNIHILATION (2015, background): “Specifically, the EGB may encompass the signatures of processes generating a truly diffuse background, like intergalactic shocks (e.g. Loeb & Waxman 2000; Miniati 2002), γ-ray emission induced by ultra-high energy cosmic rays in intergalactic space (see e.g. Bhattacharjee & Sigl 2000), and dark…”
Reviving fossil radio plasma in clusters of galaxies by adiabatic compression in environmental shock waves (2000, background): “…et al., 1997; Ryu et al., 1998), cosmic ray acceleration (Norman et al., 1995; Kang et al., 1996; Kang et al., 1997; Siemieniec and Ostrowski, 2000; Miniati et al., 2000a), gamma ray background production (Loeb and Waxman, 2000), and in probing the entropic history of the IGM (Tozzi et al., 2000).”
Detecting shock waves in cosmological smoothed particle hydrodynamics simulations (2006, background): “It has been proposed that a fraction of the diffuse cosmologicalγray background radiation originates from the same processes (Loeb & Waxman 2000; Miniati 2002; Reimer et al. 2003; Berrington & Dermer 2003; Kuo et al. 2005).”
THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV (2014, background): “There are additional theoretically well-motivated extragalactic source classes too faint to have been individually detected thus far, including galaxy clusters and their associated large scale structure formation shocks (Colafrancesco & Blasi 1998; Loeb & Waxman 2000).”
Gamma Rays from Intergalactic Shocks (2002, methodology): “This section describes the model for nonthermal emission from structure formation shocks proposed by Loeb & Waxman (2000), using simple order-of-magnitude estimates.”