从耀变体光谱中的甚高能γ射线衰减约束宇宙学参数：贝叶斯推断和系统不确定性
Constraining cosmological parameters from very-high-energy $γ$-ray attenuation in blazar spectra: Bayesian inference and systematic uncertainties
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中文总结 AI 辅助
研究利用贝叶斯推断框架，通过甚高能γ射线衰减约束宇宙学参数，结合观测驱动的EBL模型和费米-LAT目录，测量相关参数值，发现测量受EBL归一化限制，降低其不确定性可使γ射线不透明度成为\(H_0\)的有力探测手段。
中文摘要 AI 辅助
来自活跃星系核的甚高能γ射线通过在星系际背景光（EBL）上的对产生而衰减，这为宇宙膨胀提供了一种探测手段。我们开发了一个贝叶斯推断分析框架，该框架使用一个由观测驱动的、依赖红移的EBL模型，并将内在源光谱锚定到费米大面积望远镜（Fermi-LAT）的3FHL目录，同时忽略光谱形状偏差和数据集归一化。该方法在实际模拟观测中得到验证，并应用于STeVECat中汇编的50个活动星系核的241个存档高能立体视野望远镜（H.E.S.S.）、MAGIC和甚高能辐射成像望远镜阵列系统（VERITAS）光谱。由于主要的不透明度取决于EBL归一化与约化哈勃常数的比值，γ射线数据主要约束这个比值而不是单独的哈勃常数\(H_0\)。我们测量得到\(r = 1.723^{+0.096}_{-0.095}\)。对于固定的EBL尺度，这给出\(H_0 = 58.3^{+3.4}_{-3.0}\mathrm{km s^{-1} Mpc^{-1}}\)；允许18%的EBL尺度不确定性时，\(H_0 = 60.5^{+10.8}_{-10.0}\mathrm{km s^{-1} Mpc^{-1}}\)。匹配注入能无明显偏差地恢复输入不透明度，除了大的红外背景建模错误外，测试的内在光谱和EBL形状扰动是次要的。主要为低红移的样本使得\(\Omega M\)受到的约束较弱。因此，该测量受EBL归一化的限制而非统计；将其不确定性降低到百分之几将使γ射线不透明度成为对\(H_0\)具有竞争力的、独立于距离阶梯的探测手段。
英文摘要
Very-high-energy $γ$ rays from active galactic nuclei are attenuated through pair production on the extragalactic background light (EBL), providing a probe of cosmic expansion. We develop a Bayesian inference analysis framework that uses an observationally driven, redshift-dependent EBL model and anchors intrinsic source spectra to the Fermi-LAT 3FHL catalogue while marginalising spectral-shape departures and dataset normalisations. The method is validated on realistic mock observations and applied to 241 archival H.E.S.S., MAGIC and VERITAS spectra of 50 AGN compiled in STeVECat. Because the leading opacity depends on the ratio of the EBL normalisation to the reduced Hubble constant, the gamma-ray data primarily constrain this ratio rather than $H_0$ alone. We measure $r=1.723^{+0.096}_{-0.095}$. For a fixed EBL scale, this gives $H_0=58.3^{+3.4}_{-3.0},\mathrm{km,s^{-1},Mpc^{-1}}$; allowing an 18\% EBL-scale uncertainty gives $H_0=60.5^{+10.8}_{-10.0},\mathrm{km,s^{-1},Mpc^{-1}}$. Matched injections recover the input opacity without appreciable bias, and the tested intrinsic-spectrum and EBL-shape perturbations are subdominant except for large infrared-background mismodelling. The predominantly low-redshift sample leaves $Ω\mathrm{M}$ weakly constrained. The measurement is therefore limited by the EBL normalisation rather than statistics; reducing its uncertainty to a few per cent would make gamma-ray opacity a competitive, distance-ladder-independent probe of $H_0$.
