{
  "id": "1404.1189",
  "version": "v3",
  "published": "2014-04-04T09:06:09.000Z",
  "updated": "2014-08-29T17:57:13.000Z",
  "title": "Star-forming galaxies as the origin of diffuse high-energy backgrounds: Gamma-ray and neutrino connections, and implications for starburst history",
  "authors": [
    "Irene Tamborra",
    "Shin'ichiro Ando",
    "Kohta Murase"
  ],
  "comment": "26 pages, including 7 figures. Discussion expanded, new figures added. Accepted by JCAP",
  "categories": [
    "astro-ph.HE",
    "astro-ph.CO",
    "astro-ph.GA",
    "hep-ph"
  ],
  "abstract": "Star-forming galaxies have been predicted to contribute considerably to the diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Assuming that the hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos and that O(100) PeV cosmic rays can be produced and confined in starburst galaxies, we here discuss the possibility that star-forming galaxies are also the main sources of the high-energy neutrinos observed by the IceCube experiment. First, we compute the diffuse gamma-ray background from star-forming galaxies, adopting the latest Herschel PEP/HerMES luminosity function and relying on the correlation between the gamma-ray and infrared luminosities reported by Fermi observations. Then we derive the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies including normal and starburst galaxies. Our results indicate that starbursts, including those with active galactic nuclei and galaxy mergers, could be the main sources of the high-energy neutrinos observed by the IceCube experiment. We find that assuming a cosmic-ray spectral index of 2.1-2.2 for all starburst-like galaxies, our predictions can be consistent with both the Fermi and IceCube data, but larger indices readily fail to explain the observed diffuse neutrino flux. Taking the starburst high-energy spectral index as free parameter, and extrapolating from GeV to PeV energies, we find that the spectra harder than E^(-2.15) are likely to be excluded by the IceCube data, which can be more constraining than the Fermi data for this population.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2014-04-07T19:41:47.000Z",
      "abstract": "Star-forming galaxies have been predicted to contribute considerably to the isotropic diffuse gamma-ray background as they are guaranteed reservoirs of cosmic rays. Recent Fermi observations have reported the possible correlation between their gamma-ray and infrared luminosities from several galaxies identified with their gamma-ray emission. Relying on this correlation, we here compute the diffuse gamma-ray background from star-forming galaxies adopting the Herschel PEP/HerMES luminosity function up to z ~ 4. Thanks to contributions from star-forming galaxies at z > 2, we find that star-forming galaxies can explain the diffuse gamma-ray background in the 0.3-30 GeV range. We also find this result agrees with the one obtained with a simple semi-analytic model based on the star-formation rate and on templates of the Milky Way and the starbursts M82 and NGC 253. The hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos. Assuming that at least 100 PeV cosmic rays can be produced and confined in starburst galaxies, we compute the expected intensity of the diffuse high-energy neutrinos from star-forming galaxies, and conclude that starburst galaxies, including those with active galactic nuclei and galaxy mergers, could be the main contributor to the high-energy neutrinos observed by the IceCube experiment.",
      "comment": "23 pages, including 6 figures. One paragraph in Sec. 4.1 modified and one reference added; results unchanged. Comments are welcome",
      "journal": null,
      "doi": null
    },
    {
      "version": "v3",
      "updated": "2014-08-29T17:57:13.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "star-forming galaxies",
      "diffuse high-energy backgrounds",
      "diffuse gamma-ray background",
      "neutrino connections",
      "starburst history"
    ],
    "tags": [
      "journal article"
    ],
    "publication": {
      "doi": "10.1088/1475-7516/2014/09/043",
      "journal": "Journal of Cosmology and Astro-Particle Physics",
      "year": 2014,
      "month": "Sep",
      "volume": 2014,
      "number": 9,
      "pages": "043"
    },
    "note": {
      "typesetting": "TeX",
      "pages": 26,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 1288687,
      "adsabs": "2014JCAP...09..043T"
    }
  }
}