{
  "id": "1405.7047",
  "version": "v2",
  "published": "2014-05-27T20:00:16.000Z",
  "updated": "2014-10-02T18:22:16.000Z",
  "title": "New Limits On Gamma-Ray Emission From Galaxy Clusters",
  "authors": [
    "Rhiannon D. Griffin",
    "Xinyu Dai",
    "Christopher S. Kochanek"
  ],
  "comment": "5 pages, 3 figures, 2 tables, Accepted by ApJ Letters",
  "categories": [
    "astro-ph.HE",
    "astro-ph.CO"
  ],
  "abstract": "Galaxy clusters are predicted to produce gamma-rays through cosmic ray interactions and/or dark matter annihilation, potentially detectable by the Fermi Large Area Telescope (Fermi-LAT). We present a new, independent stacking analysis of Fermi-LAT photon count maps using the 78 richest nearby clusters (z<0.12) from the Two Micron All-Sky Survey (2MASS) cluster catalog. We obtain the lowest limit on the photon flux to date, 2.3e-11 ph/s/cm^2 (95% confidence) per cluster in the 0.8-100 GeV band, which corresponds to a luminosity limit of 3.5e44 ph/s. We also constrain the emission limits in a range of narrower energy bands. Scaling to recent cosmic ray acceleration and gamma-ray emission models, we find that cosmic rays represent a negligible contribution to the intra-cluster energy density and gas pressure.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2014-05-27T20:00:16.000Z",
      "abstract": "Galaxy clusters are predicted to produce gamma-rays through cosmic ray interactions and/or dark matter annihilation, potentially detectable by the Fermi Large Area Telescope (Fermi-LAT). We present a new, independent stacking analysis of Fermi-LAT photon count maps using the 79 richest nearby clusters (z<0.12) from the Two Micron All-Sky Survey (2MASS) cluster catalog. We obtain the lowest limit on the photon flux to date, 1.1e-11 ph/s/cm^2 (95% confidence) per cluster in the 0.8--100~GeV band, which corresponds to a luminosity limit of 1.7e44 ph/s. We also constrain the emission limits in a range of narrower energy bands. Scaling to recent cosmic ray acceleration and gamma-ray emission models, we find that cosmic rays represent a negligible contribution to the intra-cluster energy density and gas pressure. Furthermore, either accretion shocks must have lower Mach numbers than usually assumed (2--4) or significantly less than 50% of the baryon mass has been processed through such shocks, and thus, the majority of baryons should be assembled through minor mergers or through cold accretion.",
      "comment": "4 pages, 4 figures, 1 table, submitted to ApJ Letters",
      "journal": null,
      "doi": null
    },
    {
      "version": "v2",
      "updated": "2014-10-02T18:22:16.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "galaxy clusters",
      "fermi-lat photon count maps",
      "fermi large area telescope",
      "gamma-ray emission models",
      "cosmic ray acceleration"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/2041-8205/795/1/L21",
      "journal": "The Astrophysical Journal",
      "year": 2014,
      "month": "Nov",
      "volume": 795,
      "number": 1
    },
    "note": {
      "typesetting": "TeX",
      "pages": 5,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1298363,
      "adsabs": "2014ApJ...795L..21G"
    }
  }
}