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arXiv 0905.1115astro-ph.HEastro-ph.CO
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来自恒星和尘埃的河外背景光的模拟

Modeling the Extragalactic Background Light from Stars and Dust

Justin D. Finke, Soebur Razzaque, Charles D. Dermer

摘要:

银河系外背景光(EBL)从远红外线到可见光,延伸到紫外线,被认为是由星光主导的,无论是通过直接发射还是通过尘埃的吸收和再辐射。这是最重要的能量范围吸收$\g$ -射线从遥远的来源,如耀变体和伽马射线暴,并产生电子正电子对。在以前的工作中,我们提出了EBL模型的光学通过紫外线一贯考虑到恒星形成率(SFR),初始质量函数(IMF)和尘埃消光,并处理恒星的主要序列的黑体。这项技术被扩展到包括后主序星和星光的尘埃再处理。在我们的简单模型中,尘埃吸收的总能量被假设为在红外线中以三个黑体的形式重新发射,一个在40 K代表温暖的大尘埃颗粒,一个在70 K代表热的小尘埃颗粒,一个在450 K代表多环芳烃。我们发现我们的最佳拟合模型结合霍普金斯大学和Beacom SFR使用科尔等人的参数化与Baldry和Glazebrook IMF同意与现有的光度密度数据在各种红移。我们得到的EBL能量密度非常接近星系计数的下限,在某些情况下低于下限,并与其他最近的EBL模型的大约5 $μ$ m的短距离相当吻合。用我们的EBL模型解吸收TeV $\g$射线谱得到了与简单激波加速理论一致的结果。我们还发现,宇宙应该是光学薄的$\g$ -射线的能量小于20 GeV。

英文摘要:

The extragalactic background light (EBL) from the far infrared through the visible and extending into the ultraviolet is thought to be dominated by starlight, either through direct emission or through absorption and reradiation by dust. This is the most important energy range for absorbing $\g$-rays from distant sources such as blazars and gamma-ray bursts and producing electron positron pairs. In previous work we presented EBL models in the optical through ultraviolet by consistently taking into account the star formation rate (SFR), initial mass function (IMF) and dust extinction, and treating stars on the main sequence as blackbodies. This technique is extended to include post-main sequence stars and reprocessing of starlight by dust. In our simple model, the total energy absorbed by dust is assumed to be re-emitted as three blackbodies in the infrared, one at 40 K representing warm, large dust grains, one at 70 K representing hot, small dust grains, and one at 450 K representing polycyclic aromatic hydrocarbons. We find our best fit model combining the Hopkins and Beacom SFR using the Cole et al. parameterization with the Baldry and Glazebrook IMF agrees with available luminosity density data at a variety of redshifts. Our resulting EBL energy density is quite close to the lower limits from galaxy counts and in some cases below the lower limits, and agrees fairly well with other recent EBL models shortward of about 5 $μ$m. Deabsorbing TeV $\g$-ray spectra of various blazars with our EBL model gives results consistent with simple shock acceleration theory. We also find that the universe should be optically thin to $\g$-rays with energies less than 20 GeV.

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