Shock waves and cosmic ray acceleration in the outskirts of galaxy clusters

Hong, Sungwook E.; Ryu, Dongsu; Kang, Hyesung; Cen, Renyue

doi:10.1088/0004-637X/785/2/133

Title: Shock waves and cosmic ray acceleration in the outskirts of galaxy clusters

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Abstract

The outskirts of galaxy clusters are continuously disturbed by mergers and gas infall along filaments, which in turn induce turbulent flow motions and shock waves. We examine the properties of shocks that form within r {sub 200} in sample galaxy clusters from structure formation simulations. While most of these shocks are weak and inefficient accelerators of cosmic rays (CRs), there are a number of strong, energetic shocks which can produce large amounts of CR protons via diffusive shock acceleration. We show that the energetic shocks reside mostly in the outskirts and a substantial fraction of them are induced by infall of the warm-hot intergalactic medium from filaments. As a result, the radial profile of the CR pressure in the intracluster medium is expected to be broad, dropping off more slowly than that of the gas pressure, and might be even temporarily inverted, peaking in the outskirts. The volume-integrated momentum spectrum of CR protons inside r {sub 200} has the power-law slope of 4.25-4.5, indicating that the average Mach number of the shocks of main CR production is in the range of {sub CR} ≈ 3-4. We suggest that some radio relics with relatively flat radio spectrum could be explained bymore »« less

Authors:

Hong, Sungwook E.; Ryu, Dongsu ^[1]; Kang, Hyesung ^[2]; Cen, Renyue ^[3]

Department of Astronomy and Space Science, Chungnam National University, Daejeon 305-764 (Korea, Republic of)
Department of Earth Sciences, Pusan National University, Busan 609-735 (Korea, Republic of)
Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States)

Publication Date:: Sun Apr 20 00:00:00 EDT 2014

OSTI Identifier:: 22357090

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 785; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X

Country of Publication:: United States

Language:: English

Subject:: 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; ACCELERATORS; COSMIC RADIATION; GALAXY CLUSTERS; MACH NUMBER; PROTONS; SHOCK WAVES; SIMULATION; SPECTRA; TURBULENT FLOW

Citation Formats


                    Hong, Sungwook E., Ryu, Dongsu, Kang, Hyesung, and Cen, Renyue. Shock waves and cosmic ray acceleration in the outskirts of galaxy clusters.  United States: N. p., 2014. 
        Web.  doi:10.1088/0004-637X/785/2/133.

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                    Hong, Sungwook E., Ryu, Dongsu, Kang, Hyesung, & Cen, Renyue. Shock waves and cosmic ray acceleration in the outskirts of galaxy clusters.  United States.  https://doi.org/10.1088/0004-637X/785/2/133

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                    Hong, Sungwook E., Ryu, Dongsu, Kang, Hyesung, and Cen, Renyue. 2014.  
        "Shock waves and cosmic ray acceleration in the outskirts of galaxy clusters".  United States.  https://doi.org/10.1088/0004-637X/785/2/133.

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@article{osti_22357090,

  title        = {Shock waves and cosmic ray acceleration in the outskirts of galaxy clusters},

  author       = {Hong, Sungwook E. and Ryu, Dongsu and Kang, Hyesung and Cen, Renyue},

  abstractNote = {The outskirts of galaxy clusters are continuously disturbed by mergers and gas infall along filaments, which in turn induce turbulent flow motions and shock waves. We examine the properties of shocks that form within r {sub 200} in sample galaxy clusters from structure formation simulations. While most of these shocks are weak and inefficient accelerators of cosmic rays (CRs), there are a number of strong, energetic shocks which can produce large amounts of CR protons via diffusive shock acceleration. We show that the energetic shocks reside mostly in the outskirts and a substantial fraction of them are induced by infall of the warm-hot intergalactic medium from filaments. As a result, the radial profile of the CR pressure in the intracluster medium is expected to be broad, dropping off more slowly than that of the gas pressure, and might be even temporarily inverted, peaking in the outskirts. The volume-integrated momentum spectrum of CR protons inside r {sub 200} has the power-law slope of 4.25-4.5, indicating that the average Mach number of the shocks of main CR production is in the range of {sub CR} ≈ 3-4. We suggest that some radio relics with relatively flat radio spectrum could be explained by primary electrons accelerated by energetic infall shocks with M{sub s} ≳ 3 induced in the cluster outskirts.},

  doi          = {10.1088/0004-637X/785/2/133},

  url          = {https://www.osti.gov/biblio/22357090},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 2,

  volume       = 785,

  place        = {United States},

  year         = {Sun Apr 20 00:00:00 EDT 2014},

  month        = {Sun Apr 20 00:00:00 EDT 2014}

}

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