The Fermi gamma-ray haze from dark matter annihilations and anisotropic diffusion

Gregory Dobler, Ilias Cholis, Neal Weiner

    Research output: Contribution to journalArticle

    Abstract

    Recent full-sky maps of the Galaxy from the Fermi Gamma-Ray Space Telescope have revealed a diffuse component of emission toward the Galactic center and extending up to roughly ± 50° in latitude. This Fermi "haze" is the inverse Compton emission generated by the same electrons that generate the microwave synchrotron haze at Wilkinson Microwave Anisotropy Probe wavelengths. The gamma-ray haze has two distinct characteristics: the spectrum is significantly harder than emission elsewhere in the Galaxy and the morphology is elongated in latitude with respect to longitude with an axis ratio of ≈ 2. If these electrons are generated through annihilations of dark matter (DM) particles in the Galactic halo, this morphology is difficult to realize with a standard spherical halo and isotropic cosmic-ray (CR) diffusion. However, we show that anisotropic diffusion along ordered magnetic field lines toward the center of the Galaxy coupled with a prolate DM halo can easily yield the required morphology without making unrealistic assumptions about diffusion parameters. Furthermore, a Sommerfeld enhancement to the self-annihilation cross-section of ∼ 30 yields a good fit to the morphology, amplitude, and spectrum of both the gamma-ray and microwave haze. The model is also consistent with local CR measurements as well as cosmic microwave background constraints.

    Original languageEnglish (US)
    Article number25
    JournalAstrophysical Journal
    Volume741
    Issue number1
    DOIs
    StatePublished - Nov 1 2011

    Fingerprint

    haze
    dark matter
    gamma rays
    galaxies
    microwaves
    cosmic ray
    cosmic rays
    halos
    electron
    Microwave Anisotropy Probe
    Fermi Gamma-ray Space Telescope
    galactic halos
    longitude
    sky
    synchrotrons
    anisotropy
    electrons
    cross section
    probe
    magnetic field

    Keywords

    • astroparticle physics
    • dark matter
    • diffusion
    • Galaxy: halo
    • gamma rays: ISM

    ASJC Scopus subject areas

    • Space and Planetary Science
    • Astronomy and Astrophysics

    Cite this

    The Fermi gamma-ray haze from dark matter annihilations and anisotropic diffusion. / Dobler, Gregory; Cholis, Ilias; Weiner, Neal.

    In: Astrophysical Journal, Vol. 741, No. 1, 25, 01.11.2011.

    Research output: Contribution to journalArticle

    Dobler, Gregory ; Cholis, Ilias ; Weiner, Neal. / The Fermi gamma-ray haze from dark matter annihilations and anisotropic diffusion. In: Astrophysical Journal. 2011 ; Vol. 741, No. 1.
    @article{190af6be2dac4fe6b6346918fb822f27,
    title = "The Fermi gamma-ray haze from dark matter annihilations and anisotropic diffusion",
    abstract = "Recent full-sky maps of the Galaxy from the Fermi Gamma-Ray Space Telescope have revealed a diffuse component of emission toward the Galactic center and extending up to roughly ± 50° in latitude. This Fermi {"}haze{"} is the inverse Compton emission generated by the same electrons that generate the microwave synchrotron haze at Wilkinson Microwave Anisotropy Probe wavelengths. The gamma-ray haze has two distinct characteristics: the spectrum is significantly harder than emission elsewhere in the Galaxy and the morphology is elongated in latitude with respect to longitude with an axis ratio of ≈ 2. If these electrons are generated through annihilations of dark matter (DM) particles in the Galactic halo, this morphology is difficult to realize with a standard spherical halo and isotropic cosmic-ray (CR) diffusion. However, we show that anisotropic diffusion along ordered magnetic field lines toward the center of the Galaxy coupled with a prolate DM halo can easily yield the required morphology without making unrealistic assumptions about diffusion parameters. Furthermore, a Sommerfeld enhancement to the self-annihilation cross-section of ∼ 30 yields a good fit to the morphology, amplitude, and spectrum of both the gamma-ray and microwave haze. The model is also consistent with local CR measurements as well as cosmic microwave background constraints.",
    keywords = "astroparticle physics, dark matter, diffusion, Galaxy: halo, gamma rays: ISM",
    author = "Gregory Dobler and Ilias Cholis and Neal Weiner",
    year = "2011",
    month = "11",
    day = "1",
    doi = "10.1088/0004-637X/741/1/25",
    language = "English (US)",
    volume = "741",
    journal = "Astrophysical Journal",
    issn = "0004-637X",
    publisher = "IOP Publishing Ltd.",
    number = "1",

    }

    TY - JOUR

    T1 - The Fermi gamma-ray haze from dark matter annihilations and anisotropic diffusion

    AU - Dobler, Gregory

    AU - Cholis, Ilias

    AU - Weiner, Neal

    PY - 2011/11/1

    Y1 - 2011/11/1

    N2 - Recent full-sky maps of the Galaxy from the Fermi Gamma-Ray Space Telescope have revealed a diffuse component of emission toward the Galactic center and extending up to roughly ± 50° in latitude. This Fermi "haze" is the inverse Compton emission generated by the same electrons that generate the microwave synchrotron haze at Wilkinson Microwave Anisotropy Probe wavelengths. The gamma-ray haze has two distinct characteristics: the spectrum is significantly harder than emission elsewhere in the Galaxy and the morphology is elongated in latitude with respect to longitude with an axis ratio of ≈ 2. If these electrons are generated through annihilations of dark matter (DM) particles in the Galactic halo, this morphology is difficult to realize with a standard spherical halo and isotropic cosmic-ray (CR) diffusion. However, we show that anisotropic diffusion along ordered magnetic field lines toward the center of the Galaxy coupled with a prolate DM halo can easily yield the required morphology without making unrealistic assumptions about diffusion parameters. Furthermore, a Sommerfeld enhancement to the self-annihilation cross-section of ∼ 30 yields a good fit to the morphology, amplitude, and spectrum of both the gamma-ray and microwave haze. The model is also consistent with local CR measurements as well as cosmic microwave background constraints.

    AB - Recent full-sky maps of the Galaxy from the Fermi Gamma-Ray Space Telescope have revealed a diffuse component of emission toward the Galactic center and extending up to roughly ± 50° in latitude. This Fermi "haze" is the inverse Compton emission generated by the same electrons that generate the microwave synchrotron haze at Wilkinson Microwave Anisotropy Probe wavelengths. The gamma-ray haze has two distinct characteristics: the spectrum is significantly harder than emission elsewhere in the Galaxy and the morphology is elongated in latitude with respect to longitude with an axis ratio of ≈ 2. If these electrons are generated through annihilations of dark matter (DM) particles in the Galactic halo, this morphology is difficult to realize with a standard spherical halo and isotropic cosmic-ray (CR) diffusion. However, we show that anisotropic diffusion along ordered magnetic field lines toward the center of the Galaxy coupled with a prolate DM halo can easily yield the required morphology without making unrealistic assumptions about diffusion parameters. Furthermore, a Sommerfeld enhancement to the self-annihilation cross-section of ∼ 30 yields a good fit to the morphology, amplitude, and spectrum of both the gamma-ray and microwave haze. The model is also consistent with local CR measurements as well as cosmic microwave background constraints.

    KW - astroparticle physics

    KW - dark matter

    KW - diffusion

    KW - Galaxy: halo

    KW - gamma rays: ISM

    UR - http://www.scopus.com/inward/record.url?scp=80155182252&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=80155182252&partnerID=8YFLogxK

    U2 - 10.1088/0004-637X/741/1/25

    DO - 10.1088/0004-637X/741/1/25

    M3 - Article

    VL - 741

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 1

    M1 - 25

    ER -