Potential Contribution of Young Pulsar Wind Nebulae to Galactic High-Energy Neutrino Emission

TL;DR

This paper models the potential contribution of young pulsar wind nebulae to high-energy neutrino emission in the Galaxy, suggesting they could account for up to 5% of IceCube's observed flux at 100 TeV.

Contribution

It introduces a new population synthesis model of young PWNe considering proton transport and evolution, estimating their neutrino output and potential contribution to Galactic high-energy neutrinos.

Findings

Neutrino flux from young PWNe could reach 5% of IceCube measurements at 100 TeV.

Neutrino emission at 1 PeV strongly depends on proton injection spectra and nearby sources.

Model parameters are calibrated using the Crab nebula as a template.

Abstract

Pulsar wind nebulae (PWNe), especially the young ones, are among the most energetic astrophysical sources in the Galaxy. It is usually believed that the spin-down energy injected from the pulsars is converted into magnetic field and relativistic electrons, but the possible presence of proton acceleration inside PWNe cannot be ruled out. Previous works have estimated the neutrino emission from PWNe using various source catalogs measured in gamma-rays. However, such results rely on the sensitivity of TeV gamma-ray observations and may omit the contribution by unresolved sources. Here we estimate the potential neutrino emission from a synthetic population of PWNe in the Galaxy with a focus on the ones that are still in the free expansion phase. In the calculation, we model the temporal evolution of the free-expanding PWNe and consider the transport of protons inside the PWNe. The Crab nebula is treated as a standard template for young PWNe to evaluate some model parameters, such as the energy conversion fraction of relativistic protons and the target gas density for the hadronic process, which are relevant to neutrino production. In the optimistic case, the neutrino flux from the simulated young PWNe may constitute to 5% of the measured flux by IceCube around 100 TeV. At higher energy around 1 PeV, the neutrino emission from the population highly depends on the injection spectral shape, and also on the emission of the nearby prominent sources.