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Cumulative neutrino background from quasar-driven outflows

Quasar-driven outflows naturally account for the missing component of the extragalactic $γ$-ray background through neutral pion production in interactions between protons accelerated by the forward outflow shock and interstellar protons. We study the simultaneous neutrino emission by the same protons. We adopt outflow parameters that best fit the extragalactic $γ$-ray background data and derive a cumulative neutrino background of $\sim10^{-7}\,\rm GeV\,cm^{-2}\,s^{-1}\,sr^{-1}$ at neutrino energies $E_ν\gtrsim 10$ TeV, which naturally explains the most recent IceCube data without tuning any free parameters. The link between the $γ$-ray and neutrino emission from quasar outflows can be used to constrain the high-energy physics of strong shocks at cosmological distances.