Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays
Intergalactic Photon Spectra from the Far-IR to the UV Lyman Limit for 0 < z < 6 and the Optical Depth of the Universe to High-Energy Gamma Rays
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DOI：
10.1086/506188
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发表时间：
2005-10
期刊：
影响因子：
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通讯作者：
F. Stecker;F. Stecker;M. Malkan;S. Scully
中科院分区：
文献类型：
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作者：
F. Stecker;F. Stecker;M. Malkan;S. Scully
我们计算了Λcdm宇宙中0<；z<；6的星际光子密度，它是能量和红移的函数，光子能量从.003 eV到13.6 eV的莱曼极限截止值，ΩΛ=0.7，Ωm=0.3。我们的星系反向演化模型的基本特征是由Malkan&Stecker在早期的论文中提出的。经过一些改进，我们发现这个演化模型给出了来自Spitzer的新的深数计数的预测，以及漫射红外背景的光谱能量分布的计算，与数据吻合得很好。然后，我们使用计算的星系间光子密度来扩展之前关于星系际空间中高能γ射线的吸收的工作，这是由于与低能光子和2.7K宇宙微波背景辐射的相互作用。我们计算了红移从0到5的源发射的能量从4GeV到100TeV的γ射线的宇宙光学厚度τ，并给出了近似τ(Eγ，z)的解析拟合和数值系数。作为结果应用的一个例子，我们计算了blazar PKS2155-304z=0.117的吸收光谱，并与Hess air Cerenkovγ-ray望远镜阵列观测到的光谱进行了比较。
We calculate the intergalactic photon density as a function of both energy and redshift for 0 < z < 6 for photon energies from.003 eV to the Lyman limit cutoff at 13.6 eV in a ΛCDM universe with ΩΛ = 0.7 and Ωm = 0.3. The basic features of our backward-evolution model for galaxies were developed in earlier papers by Malkan & Stecker. With a few improvements, we find that this evolutionary model gives predictions of new deep number counts from Spitzer, as well as a calculation of the spectral energy distribution of the diffuse infrared background, which are in good agreement with the data. We then use our calculated intergalactic photon densities to extend previous work on the absorption of high-energy γ-rays in intergalactic space owing to interactions with low-energy photons and the 2.7 K cosmic microwave background radiation. We calculate the optical depth of the universe, τ, for γ-rays having energies from 4 GeV to 100 TeV emitted by sources at redshifts from 0 to 5. We also give an analytic fit with numerical coefficients for approximating τ(Eγ, z). As an example of the application of our results, we calculate the absorbed spectrum of the blazar PKS 2155-304 at z = 0.117 and compare it with the spectrum observed by the HESS air Cerenkov γ-ray telescope array.