标题： 低光度AGN在NGC 4278中的极高能伽马射线辐射的强子起源 显示英文标题

标题： Hadronic origin of the very high-energy gamma-ray emission from the low-luminosity AGN in NGC 4278

摘要： 大型高海拔空气簇射观测站已探测到来自NGC 4278的极高能(VHE)伽马射线，该天体已知拥有一个低光度活动星系核(AGN)。由于其无线电喷流非常微弱，其VHE伽马射线的起源尚不明确。在本文中，我们首先通过分析使用阿塔卡马大型毫米波/亚毫米波阵列获得的数据，表明NGC 4278有一个巨大的分子云围绕着核心。然后我们假设宇宙射线质子在超大质量黑洞周围的辐射无效吸积流中被加速，并扩散到分子云中，通过$pp$相互作用产生伽马射线和中微子。我们对伽马射线谱进行了建模，发现如果AGN活动在过去比现在更高，并且分子云中的扩散系数明显小于银河系星际介质中的扩散系数，那么观测结果可以通过这种强子过程来解释。然而，我们还表明，与伽马射线共同产生的高能中微子即使使用IceCube-Gen2也极不可能被探测到。 显示英文摘要

摘要： The Large High Altitude Air Shower Observatory has detected very high-energy (VHE) gamma rays from NGC 4278, which is known to host a low-luminosity active galactic nucleus (AGN). Having only very weak radio jets, the origin of its VHE gamma rays is unclear. In this paper we first show that NGC 4278 has a massive molecular cloud surrounding the nucleus by analyzing data taken with the Atacama Large Millimeter/submillimeter Array. We then assume that cosmic ray protons are accelerated in a radiatively inefficient accretion flow around the supermassive black hole, which diffuse into the molecular cloud and produce gamma rays and neutrinos via $pp$ interactions. We model the gamma-ray spectra and find that the observations can be explained by such hadronic processes if the AGN activity was higher in the past than at present, and the diffusion coefficient in the molecular cloud is appreciably smaller than in the Milky Way interstellar medium. However, we also show that the high-energy neutrinos co-produced with the gamma rays are unlikely to be detectable even with IceCube-Gen2.