The astrophysics community is considering plans for a variety of gamma-ray telescopes (including ACT and GRIPS) in the energy range 1--100 MeV, which can fill in the so-called "MeV gap" in current sensitivity. We investigate the utility of such detectors for the study of low-mass dark matter annihilation or decay. For annihilating (decaying) dark matter with a mass below about 140 MeV (280 MeV) and couplings to first generation quarks, the final states will be dominated by photons or neutral pions, producing striking signals in gamma-ray telescopes. We determine the sensitivity of future detectors to the kinematically allowed final states. In particular, we find that planned detectors can improve on current sensitivity to this class of models by up to a few orders of magnitude.
Mysteries about the origin of high-energy cosmic neutrinos have deepened by the recent IceCube measurement of a large diffuse flux in the 10-100 TeV range. Based on the standard disk-corona picture of active galactic nuclei (AGN), we present a phenomenological model enabling us to systematically calculate the spectral sequence of multimessenger emission from the AGN coronae. We show that protons in the coronal plasma can be stochastically accelerated up to PeV energies by plasma turbulence, and find that the model explains the large diffuse flux of medium-energy neutrinos if the cosmic rays ca…
Neutral hydrogen (HI) intensity mapping traces the large-scale distribution of matter in the Universe and therefore should correlate with the gamma-ray emission originated from particle dark matter annihilation or from active galactic nuclei and star-forming galaxies, since the related processes occur in the same cosmic structures hosting HI. In this paper, we derive the cross-correlation signal between the brightness temperature of the 21-cm line emission of the HI spin-flip transition in the Universe and the unresolved gamma-ray background. Specifically, we derive forecasts for the cross-cor…
An Electron-Tracking Compton Telescope for a Survey of the Deep Universe by MeV gamma-rays
MeV γ射线的光子成像由于背景大、图像不清晰而存在严重困难,其原因是探测中康普顿散射的物理参数确定不完整,缺乏反冲电子的方向信息。最近在MeV波段的主要飞行任务/仪器是康普顿伽马射线观测台/COMPTEL,它是康普顿照相机(CC),只探测到了$\sim30$持久源。它与GeV波段的$\sim$ 2000源形成鲜明对比。在这里,我们报告的电子跟踪康普顿相机(ETCC)的性能,并证明它有一个很好的潜力,以突破这一停滞在MeV的伽玛射线天文学。ETCC通过测量3-D反冲电子径迹提供康普顿散射的所有参数,然后恢复在CC中丢失的散射面偏差(SPD)。的能量损失率(dE/dx),其中CC无法测量,也得到了,并发现确实有助于减少背景下类似的空间条件下。因此,伽马检测的重要性提高了几倍。另一方面,SPD是定量确定点扩散函数(PSF)的必要条件。对于反冲电子的多次散射,SPD的分辨率提高到接近理论极限。有了这样一个良好确定的PSF,我们证明了第一次,它是可能的,以提供可靠的灵敏度在康普顿成像,而不利用优化算法。因此,这项研究突出了CC的根本弱点。相反,我们证明了ETCC在1 MeV下达到低于$1\times10^{-12}$ erg cm $^{-2}$ s $^{-1}$的灵敏度的可能性。