Neutrino events at IceCube and the Fermi bubbles

Abstract

We discuss the possibility that the IceCube neutrino telescope might be observing the Fermi bubbles. If the bubbles discovered in gamma rays originate from accelerated protons, they should be strong emitters of high energy (≳GeV) neutrinos. These neutrinos are detectable as showerlike or tracklike events at a Km 3 neutrino observatory. For a primary cosmic ray flux with spectrum ∝ E −2.1 and cutoff energy at or above 10 PeV, the Fermi bubble flux substantially exceeds the atmospheric background, and could account for up to ∼4-5 of the 28 events detected above ∼30 TeV at IceCube. Running the detector for ∼5-7 more years should be sufficient to discover this flux at high significance. For a primary cosmic ray flux with steeper spectrum, and/or lower cutoff energy, longer running times will be required to overcome the background.

Observation of High-Energy Astrophysical Neutrinos in Three Years of IceCube Data

“…Exceptions may be made for local large diffuse sources (e.g., the Fermi bubbles [41] or the Galactic Halo [42,43]), but these models can typically explain, at most, a fraction of the data. If our data arise from an extragalactic flux produced by many isotropically distributed point sources, we can compare our all-sky flux with existing point-source limits.…”

Astrophysical origin of high-energy cosmic neutrinos

“…It has been suggested that this emission is caused by pp interactions of CRs that are injected from the Galactic center fort ∼ 1 − 10 Gyr [82]. In this model, the neutrino flux suggested from fluctuations around the Fermi bubbles can be consistent with a a power index s ν ≈ 2.2 [23,83]. On the other hand, the leptonic emission model is also viable that seems more consistent with the recent indication of a high-energy gamma-ray cutoff [84].…”

Multi-Messenger Aspects of Cosmic Neutrinos

“…However, the limited event statistics of the samples leave some room for Galactic contributions. Possible Galactic contributions to super-TeV neutrinos are the diffuse neutrino emission of galactic CRs [11,12,13], the joint emission of galactic PeV sources [14,15] or microquasars [16], and extended galactic structures like the Fermi Bubbles [17,11,18] or the Galactic halo [19]. A possible association with the sub-TeV diffuse galactic gamma-ray emission [20] and constraints from the non-observation of diffuse galactic PeV gamma-rays [21,11], have also been investigated.…”