Center for Cosmology and AstroParticle Physics (CCAPP), and Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA.
Phys Rev Lett. 2018 Mar 23;120(12):121101. doi: 10.1103/PhysRevLett.120.121101.
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 of hadronic γ-ray production, and has been named the "TeV excess." We show that TeV emission from pulsars naturally explains this excess. Recent observations have detected "TeV halos" surrounding pulsars that are either nearby or particularly luminous. Extrapolating this emission to the full population of Milky Way pulsars indicates that the ensemble of "subthreshold" sources necessarily produces bright TeV emission diffusively along the Milky Way plane. Models indicate that the TeV halo γ-ray flux exceeds that from hadronic γ rays above an energy of ∼500 GeV. Moreover, the spectrum and intensity of TeV halo emission naturally matches the TeV excess. 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.
Milagro 观测发现，明亮的弥散 TeV 发射集中在银河系的银盘上。目前的强子 γ射线产生模型很难解释这种发射的强度和光谱，因此被称为“TeV 过剩”。我们表明，脉冲星的 TeV 发射自然可以解释这种过剩。最近的观测已经探测到围绕脉冲星的“TeV 晕”，这些脉冲星要么在附近，要么特别亮。将这种发射扩展到银河系中所有脉冲星的种群，表明“亚阈值”源的总体必然会在银河系平面上产生明亮的弥散 TeV 发射。模型表明，TeV 晕的 γ射线通量在超过 500 GeV 的能量上超过了强子 γ射线。此外，TeV 晕发射的光谱和强度与 TeV 过剩自然匹配。最后，我们表明，即将到来的 HAWC 观测将把 TeV 过剩的很大一部分解析为单个 TeV 晕，从而明确证实或排除这一模型。
