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arXiv 0912.4156astro-ph.HE
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星系中的宇宙射线:恒星形成的探测

Cosmic rays in galaxies: a probe of star formation

Massimo Persic, Yoel Rephaeli

摘要:

在星暴星系中心区域的宇宙射线能量密度,分别由射电和伽马射线测量的非热同步辐射和中性π介子衰变辐射推断,通常是U_p = O(100)eV/cm 3,也就是说,通常至少比银河系中心附近和其他恒星形成不太活跃的星系大一个数量级。我们首先表明,这些非常不同的能量密度水平反映了两种环境中各自超新星发生率的相似差异,考虑到(银河系)高能粒子的超新星起源,这并不意外。作为这种对应的结果,我们证明,有部分定量的证据表明,恒星初始质量函数(IMF)在星暴核具有低质量截断在~2M_sun,湍流介质的理论模型所预测的,与0.1M_sun的小得多的值,其特征在于低质量截断的恒星IMF在“正常”银河系环境。

英文摘要:

Cosmic-ray energy densities in central regions of starburst galaxies, as inferred from radio and gamma-ray measurements of, respectively, non-thermal synchrotron and neutral pion decay emission, are typically U_p = O(100)eV/cm3, i.e. typically at least an order of magnitude larger than near the Galactic center and in other non-very-actively star-forming galaxies. We first show that these very different energy-density levels reflect a similar disparity in the respective supernova rates in the two environments, which is not unexpected given the supernova origin of (Galactic) energetic particles. As a consequence of this correspondence, we then demonstrate that there is partial quantitative evidence that the stellar initial mass function (IMF) in starburst nuclei has a low-mass truncation at ~2M_sun, as predicted by theoretical models of turbulent media, in contrast with the much smaller value of 0.1M_sun that characterizes the low-mass cutoff of the stellar IMF in `normal' galactic environments.

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