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arXiv 1101.3498astro-ph.CO
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近中红外河外背景光的强新约束

Strong New Constraints on the Extragalactic Background Light in the Near- to Mid-IR

Matthew Orr, Frank Krennrich, Eli Dwek

摘要:

直接测量河外背景光(EBL)在近红外到中红外波段是非常困难的,因为来自黄道光的压倒性前景比微弱的宇宙学漫射辐射场亮了一个数量级以上。活动星系核的γ射线观测提供了对EBL的间接约束。使用费米伽马射线空间望远镜与当前一代地基切伦科夫望远镜(H.E.S.S.,MAGIC和VERITAS)提供了前所未有的灵敏度和光谱覆盖范围的限制EBL在近中红外。在本文中,我们提出了新的限制EBL的基础上的宽频带光谱的一组选择的伽马射线耀变体,覆盖200兆电子伏到几个TeV的分析。15微米处的EBL强度被限制为1.36 +/- 0.58 nW m^-2 sr^-1。我们发现Stecker等人(2006)的快速演化和基线EBL模型以及Kneiske等人(2004)的模型预测中红外(15微米)的EBL强度明显高于此处推导的约束条件所允许的强度。此外,Franceschini等人(2008)的模型和Dominguez等人(2011)的基准模型预测的近中IR比率小于我们的分析预测的比率。即,它们在近IR中的强度太低,而它们在中IR中的强度稍微太高。所有上述模型都与我们在>3 sigma水平上的分析不一致。

英文摘要:

Direct measurements of the extragalactic background light (EBL) in the near-IR to mid-IR waveband are extremely difficult due to an overwhelming foreground from the zodiacal light that outshines the faint cosmological diffuse radiation field by more than an order of magnitude. Indirect constraints on the EBL are provided by gamma-ray observations of AGN. Using the combination of the Fermi Gamma-Ray Space Telescope together with the current generation of ground-based air Cherenkov telescopes (H.E.S.S., MAGIC, and VERITAS) provides unprecedented sensitivity and spectral coverage for constraining the EBL in the near- to mid-IR. In this paper we present new limits on the EBL based on the analysis of the broad-band spectra of a select set of gamma-ray blazars covering 200 MeV to several TeV. The EBL intensity at 15 microns is constrained to be 1.36 +/- 0.58 nW m^-2 sr^-1. We find that the fast evolution and baseline EBL models of Stecker et al. (2006), as well as the model of Kneiske et al. (2004), predict significantly higher EBL intensities in the mid-IR (15 microns) than is allowed by the constraints derived here. In addition, the model of Franceschini et al. (2008) and the fiducial model of Dominguez et al. (2011) predict near- to mid-IR ratios smaller than that predicted by our analysis. Namely, their intensities in the near-IR are too low while their intensities in the mid-IR are marginally too high. All of the aforementioned models are inconsistent with our analysis at the >3 sigma level.

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