标题： VHE$γ$射线通量的上限来自ULIRG Arp 220和其他星系的VERITAS 显示英文标题

标题： Upper limits on the VHE $γ$-ray flux from the ULIRG Arp 220 and other galaxies with VERITAS

摘要： 超亮红外星系（ULIRGs）的核心是非常密集的环境，具有高恒星形成率和超新星爆发率。 它们被认为是宇宙射线加速的场所，并被预测在GeV到TeV范围内发射$\gamma$-rays。 到目前为止，还没有在$\gamma$-rays中检测到任何ULIRG。 距离地球最近的ULIRG Arp 220已经得到了深入研究，该星系中$\gamma$-ray产生的详细模型也已存在。 它们预测在几个TeV范围内，$\gamma$-ray谱较为坚硬。 由于其高恒星形成率、高气体密度以及距离地球较近，Arp 220被认为是非常适合观测极高能（VHE；100 GeV - 100 TeV）$\gamma$-rays的优良候选者。 Arp 220由VERITAS望远镜观测了超过30小时，没有发现超过宇宙射线背景的显著过量。 从这些观测中得出的Arp 220的VHE$\gamma$-ray通量上限是迄今为止提出的最敏感的限制，并开始对理论模型进行约束。 我们还提供了超亮红外星系IRAS 17204-0014、星暴星系IC 342和活动星系3C321的VHE通量上限。 显示英文摘要

摘要： The cores of ultra-luminous infrared galaxies (ULIRGs) are very dense environments, with a high rate of star formation and supernova explosions. They are thought to be sites of cosmic-ray acceleration, and are predicted to emit $\gamma$-rays in the GeV to TeV range. So far, no ULIRG has been detected in $\gamma$-rays. Arp 220, the closest ULIRG to Earth, has been well studied, and detailed models of $\gamma$-ray production in this galaxy are available. They predict a rather hard $\gamma$-ray spectrum up to several TeV. Due to its large rate of star formation, high gas density, and its close proximity to Earth, Arp 220 is thought to be a very good candidate for observations in very-high-energy (VHE; 100 GeV - 100 TeV) $\gamma$-rays. Arp 220 was observed by the VERITAS telescopes for more than 30 hours with no significant excess over the cosmic-ray background. The upper limits on the VHE $\gamma$-ray flux of Arp 220 derived from these observations are the most sensitive limits presented so far and are starting to constrain theoretical models. We also present upper limits for the VHE flux from the ULIRG IRAS 17204-0014, the starburst galaxy IC 342, and the active galaxy 3C321.