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arXiv 1102.5095astro-ph.HEastro-ph.GAhep-ph
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来自暗物质湮灭和各向异性扩散的费米Gamma-Ray雾

The Fermi Gamma-Ray Haze from Dark Matter Annihilations and Anisotropic Diffusion

Gregory Dobler, Ilias Cholis, Neal Weiner

摘要:

最近费米伽马射线太空望远镜拍摄的银河系全天空图显示了一个朝向银河系中心的弥散辐射成分,并延伸到大约+/-50度的纬度。这种费米“雾”是由在WMAP波长处产生微波同步加速器雾的相同电子产生的逆康普顿发射。伽马射线雾有两个明显的特征:光谱明显比银河系其他地方的发射更硬,并且形态在纬度上相对于经度被拉长,轴比约为2。如果这些电子是通过星系晕中暗物质粒子的湮灭产生的,那么这种形态很难用标准的球形晕和各向同性的宇宙射线扩散来实现。然而,我们表明,各向异性扩散沿有序的磁场线对银河系中心加上一个长形的暗物质晕可以很容易地产生所需的形态,而不作出不切实际的假设扩散参数。此外,索末菲增强的自湮没截面~30产生了很好的拟合的伽马射线和微波雾的形态,振幅和光谱。该模型也是符合当地的宇宙射线测量以及CMB的限制。

英文摘要:

Recent full-sky maps of the Galaxy from the Fermi Gamma-Ray Space Telescope have revealed a diffuse component of emission towards the Galactic center and extending up to roughly +/-50 degrees in latitude. This Fermi "haze" is the inverse Compton emission generated by the same electrons which generate the microwave synchrotron haze at WMAP 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 ~2. If these electrons are generated through annihilations of dark matter particles in the Galactic halo, this morphology is difficult to realize with a standard spherical halo and isotropic cosmic-ray diffusion. However, we show that anisotropic diffusion along ordered magnetic field lines towards the center of the Galaxy coupled with a prolate dark matter 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 cosmic-ray measurements as well as CMB constraints.

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