Abstract
The recent discovery of a diffuse neutrino flux up to PeV energies raises the question of which populations of astrophysical sources contribute to this diffuse signal. One extragalactic candidate source population to produce high-energy neutrinos are Blazars. We present results from a likelihood analysis searching for cumulative neutrino emission from Blazar populations selected with the 2nd Fermi-LAT AGN catalog (2LAC) using an IceCube data set that has been optimized for the detection of individual sources. In contrast to previous searches with IceCube, the investigated populations contain up to hundreds of sources, the biggest one being the entire Blazar sample measured by the Fermi-LAT. No significant neutrino signal was found from any of these populations. Some implications of this non-observation for the origin of the observed PeV diffuse signal will be discussed.
Highlights
In 2013, the IceCube collaboration reported on the detection of an astrophysical diffuse neutrino flux in the 40 TeV–2 PeV energy range [1]
We present results from a likelihood analysis searching for cumulative neutrino emission from Blazar populations selected with the 2nd Fermi LAT active galactic nuclei (AGN) catalogue (2LAC) using an IceCube data set that has been optimized for the detection of individual sources
An experimental approach is presented here to answer the question if the Blazars that dominate the high energy energies and above (EGB) emission produce a large fraction of the astrophysical neutrino flux
Summary
In 2013, the IceCube collaboration reported on the detection of an astrophysical diffuse neutrino flux in the 40 TeV–2 PeV energy range [1]. Neutrino emission from Blazars has been discussed extensively in hadronic jet models originating from p-p or p- interactions The extragalactic non-thermal radiation background at GeV energies and above (EGB) is dominated by the emission from Blazars [4]. An experimental approach is presented here to answer the question if the Blazars that dominate the high energy EGB emission produce a large fraction of the astrophysical neutrino flux. The idea is to look for directional clustering in a large sample of muon tracks collected by IceCube, around the directions of gamma-ray sources associated with Blazars in the Fermi-2LAC catalog [5]. Assumptions about the relative contributions (“weights”) of the individual sources within the population.
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