Theγ-ray emitting region in low synchrotron peak blazars
Theγ-ray emitting region in low synchrotron peak blazars
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DOI：
10.1051/0004-6361/201833005
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发表时间：
2018-04
影响因子：
6.5
通讯作者：
B. Arsioli;Y-L. Chang
中科院分区：
文献类型：
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作者：
B. Arsioli;Y-L. Chang
目标。从γ射线天文学的早期开始，在活动星系核（AGN）的核心定位GeV发射的起源一直是一个悬而未决的问题；问题是根据与超大质量中央发动机的距离来区分近地点和远地点。我们在低同步加速器峰值（LSP）耀变体的完整样本下研究了这个问题，该耀变体在电磁波谱中具有几十年的完整特征，从无线电到数十GeV。我们考虑了明亮射电blazar的高能发射，并在定位γ射线发射点的框架下对同步加速器自康普顿（SSC）和外部康普顿（EC）场景进行了测试。考虑到EC体制下的逆康普顿（IC）过程是由外部种子光子的丰度驱动的，这些光子可能主要是来自吸积盘区域和宽线区域（BLR）的紫外线（UV）到x射线，因此靠近喷气发射基地；或来自尘埃环面和分子云脊鞘的红外（IR）种子光子，因此远离喷气机发射基地。本文研究了这两种情景，并试图揭示agn中γ射线辐射产生背后的物理原理，这对确定产生地点至关重要。方法：基于104个射电选择的37 GHz通量密度高于1 Jy的LSP blazar的完整样本，我们研究了与非热射流发射过程相关的宽带种群特性，并测试了SSC和EC情景解释整体光谱能量分布（SED）特征的能力。考虑到目前所有可用的数据，我们使用的SEDs具有从射电到γ射线的良好特征。从最近的工作中获得的增强的可用信息使我们能够改进Syn与IC峰相关性的研究，它指向一个特定的γ射线发射位点。结果表明，单靠SSC不足以解释观测到的SEDs。我们的分析倾向于汤姆逊散射下的EC情景，主要是红外外光子场。因此，在用纯轻子分量建模的情况下，远点（即远离喷射发射）可能是解释明亮LSP耀变体的总体特性的最合理的情况。我们计算出射流运动坐标系下与外场相关的光子能量密度为1.69 × 10−2erg cm−3，与其他相关研究结果吻合较好。
Aims.From the early days inγ-ray astronomy, locating the origin of GeV emission within the core of an active galactic nucleus (AGN) persisted as an open question; the problem is to discern between near- and far-site scenarios with respect to the distance from the super massive central engine. We investigate this question under the light of a complete sample of low synchrotron peak (LSP) blazars which is fully characterized along many decades in the electromagnetic spectrum, from radio up to tens of GeV. We consider the high-energy emission from bright radio blazars and test for synchrotron self-Compton (SSC) and external Compton (EC) scenarios in the framework of localizing theγ-ray emission sites. Given that the inverse Compton (IC) process under the EC regime is driven by the abundance of external seed photons, these photons could be mainly ultraviolet (UV) to X-rays coming from the accretion disk region and the broad-line region (BLR), therefore close to the jet launch base; or infrared (IR) seed photons from the dust torus and molecular cloud spine-sheath, therefore far from jet launch base. We investigate both scenarios, and try to reveal the physics behind the production ofγ-ray radiation in AGNs which is crucial in order to locate the production site.Methods.Based on a complete sample of 104 radio-selected LSP blazars, with 37 GHz flux density higher than 1 Jy, we study broadband population properties associated with the nonthermal jet emission process, and test the capability of SSC and EC scenarios to explain the overall spectral energy distribution (SED) features. We use SEDs well characterized from radio toγrays, considering all currently available data. The enhanced available information from recent works allows us to refine the study of Syn to IC peak correlations, which points to a particularγ-ray emission site.Results.We show that SSC alone is not enough to account for the observed SEDs. Our analysis favors an EC scenario under the Thomson scattering regime, with a dominant IR external photon field. Therefore, the far-site (i.e., far from the jet launch) is probably the most reasonable scenario to account for the population properties of bright LSP blazars in cases modeled with a pure leptonic component. We calculate the photon energy density associated with the external field at the jet comoving frame to beU′ext= 1.69 × 10−2erg cm−3, finding good agreement to other correlated works.