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arXiv 0909.0222astro-ph.HE
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来自恒星形成区的伽马射线:从SNOB到暗加速器

Gamma-rays from star-forming regions: from SNOBs to dark accelerators

Thierry Montmerle

摘要:

观测伽马射线天文学诞生于大约40年前,当时小型探测器在卫星上飞行,经过十年的理论预测,它有可能通过π-零衰变机制发现宇宙射线的起源。70年代是伽马射线和宇宙射线天体物理学的黄金时代,宇宙射线的“扩散激波加速”理论被(重新)发现,第一次对银道面进行CO和GeV伽马射线巡天,验证了π-零衰变在银河系大规模伽马射线发射中的重要性。但由于这种强烈的银河系背景,GeV伽马射线源很难识别。第一个被确定的伽马射线源是三颗超新星,这表明超新星遗迹与大质量恒星形成区(“SNOB”)中的分子云相互作用也是伽马射线源。由于其灵敏度和空间分辨率的提高,地基切伦科夫望远镜,检测伽马射线在> TeV的能量,现在能够解决分子云大小的物体在几个千秒差距。像IC 443和W28这样的SNOB物体在GeV和TeV能量下被探测到,并显示了SNR冲击波和附近分子云之间宇宙射线相互作用的空间证据,以及随后的π-零衰变。然而,光谱证据并不清楚地支持这一机制。我们建议使用另一种工具来探测假定的本地宇宙射线的低能量分量的相互作用,在TeV明亮的分子云的增强电离的形式,使用毫米观测。

英文摘要:

Observational gamma-ray astronomy was born some forty years ago, when small detectors were flown in satellites, following a decade of theoretical predictions of its potential to discover the origin of cosmic rays via the pi-zero decay mechanism. The seventies were a golden era for gamma-ray and cosmic-ray astrophysics, with the (re)discovery of the "diffuse shock acceleration" theory for cosmic rays, and the first CO and GeV gamma-ray surveys of the galactic plane, verifying the importance of pi-zero decay in the large-scale gamma-ray emission of the Galaxy. But because of this strong galactic background, GeV gamma-ray sources were hard to identify. The first such sources definitely identified were three pulsars, with a suggestion that supernova remnants interacting with molecular clouds in massive star-forming regions ("SNOBs") were also gamma-ray sources. Because of their improved sensitivity and spatial resolution, ground-based Cerenkov telescopes, detecting gamma-rays at > TeV energies, are now able to resolve molecular cloud-sized objects at a few kpc. SNOB-like objects like IC443 and W28 are detected at GeV and TeV energies, and show spatial evidence for cosmic-ray interactions between an SNR shock wave and nearby molecular clouds, and subsequent pi-zero decay. However, the spectral evidence does not clearly support this mechanism. We propose to use another tool for probing the interaction of the low-energy component of the putative local cosmic rays, in the form of enhanced ionization in TeV-bright molecular clouds, using millimeter observations.

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