FLUX AND PHOTON SPECTRAL INDEX DISTRIBUTIONS OF FERMI-LAT BLAZARS AND CONTRIBUTION TO THE EXTRAGALACTIC GAMMA-RAY BACKGROUND
FLUX AND PHOTON SPECTRAL INDEX DISTRIBUTIONS OF FERMI-LAT BLAZARS AND CONTRIBUTION TO THE EXTRAGALACTIC GAMMA-RAY BACKGROUND
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DOI：
10.1088/0004-637x/753/1/45
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发表时间：
2011-06
期刊：
影响因子：
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通讯作者：
J. Singal;V. Petrosian;M. Ajello
中科院分区：
文献类型：
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作者：
J. Singal;V. Petrosian;M. Ajello
我们给出了用费米伽马射线太空望远镜的大面积望远镜在第一年星表中探测到的352颗闪耀星的光子能谱指数和伽马射线通量的分布--所谓的对数N-对数S关系--其探测阈值大于约7σ，位于银河纬度±20°以上。由于通量探测阈值依赖于光子指数，因此观测到的原始分布不能提供真实的对数N-对数S计数或光子指数的真实分布。我们使用Efron和Petrosian发展的非参数方法从观测数据中重建本征分布，它解释了由观测偏差引入的数据截断，并包括了两个变量之间可能的相关性的影响。我们用Blazar的模拟数据集演示了我们方法的稳健性，并将这些方法应用于实际数据，发现对于整个种群而言，内禀通量分布可以用一个破缺的幂定律来表示，其高、低指数分别为−2.37±0.13和−1.70±0.26，本征光子折射率分布可以用均值为2.41±0.13、宽度为0.25±0.03的高斯分布来表示。我们还分别找到了BLLac和平谱射电类星体blazar的子群的内禀分布。然后，我们计算了费米耀星对漫射河外伽马射线背景辐射的贡献。在假设blazar的通量分布继续保持任意低通量的情况下，我们计算了所有blazar对河外伽马射线输出的最佳拟合贡献为60%，具有很大的不确定性。
We present a determination of the distributions of the photon spectral index and gamma-ray flux—the so-called log N–log S relation—for the 352 blazars detected with a greater than approximately 7σ detection threshold and located above ±20° Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true log N–log S counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstruct the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation between the two variables. We demonstrate the robustness of our procedures using a simulated data set of blazars and then apply these to the real data and find that for the population as a whole the intrinsic flux distribution can be represented by a broken power law with high and low indices of −2.37 ± 0.13 and −1.70 ± 0.26, respectively, and the intrinsic photon index distribution can be represented by a Gaussian with mean of 2.41 ± 0.13 and width of 0.25 ± 0.03. We also find the intrinsic distributions for the sub-populations of BL Lac and flat spectrum radio quasar type blazars separately. We then calculate the contribution of Fermi blazars to the diffuse extragalactic gamma-ray background radiation. Under the assumption that the flux distribution of blazars continues to arbitrarily low fluxes, we calculate the best-fit contribution of all blazars to the total extragalactic gamma-ray output to be 60%, with a large uncertainty.