Pulsar TeV Halos Explain the TeV Excess Observed by Milagro

TL;DR

This paper proposes that TeV halos around pulsars can explain the diffuse TeV gamma-ray excess observed by Milagro, providing a natural astrophysical source that matches the observed spectrum and intensity.

Contribution

It introduces the idea that pulsar TeV halos account for the TeV excess, linking recent halo observations to the diffuse emission along the galactic plane.

Findings

TeV halos' gamma-ray flux exceeds hadronic flux above 500 GeV.

The spectrum and intensity of TeV halos match the observed TeV excess.

Upcoming HAWC observations can confirm the halo contribution.

Abstract

Milagro observations have found bright, diffuse TeV emission concentrated along the galactic plane of the Milky Way. The intensity and spectrum of this emission is difficult to explain with current models where gamma-ray production is dominated by hadronic mechanisms, and has been named the "TeV excess". We show that TeV emission from pulsars naturally explains this excess. In particular, recent observations have detected "TeV halos" surrounding pulsars that are either nearby or particularly luminous. Here, we show that the full population of Milky Way pulsars will produce diffuse TeV emission concentrated along the Milky Way plane. The total gamma-ray flux from TeV halos is expected to exceed the hadronic gamma-ray flux at energies above ~500 GeV. Moreover, the spectrum and intensity of TeV halo emission naturally matches the TeV excess. If this scenario is common to all galaxies, it will decrease the contribution of star-forming galaxies to the IceCube neutrino flux. Finally, we show that upcoming HAWC observations will resolve a significant fraction of the TeV excess into individual TeV halos, conclusively confirming, or ruling out, this model.