发表机构
Institut d’Astrophysique et de Géophysique, Université de Liège（列日大学天体物理与地球物理研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究活动星系核宽发射线在高低吸积系统中减弱或消失的现象，提出由电离辐射场经过滤后到达宽线区来决定谱线形成，统一了相关现象并解释了一些效应。
AI 中文摘要
宽发射线是活动星系核的一个显著特征，但在极低和极高吸积系统中会减弱或消失。通常分别处理这些情况，尚未有统一物理解释。本文表明若谱线形成由中心引擎的固有光度而非到达宽线区前经过滤的电离辐射场决定，就会出现这种行为。此框架统一了低光度活动星系核、低电离核发射线区星系和弱线类星体中宽发射线的缺失或极微弱现象，并解释了鲍德温效应和铁离子丰度趋势。它还意味着在极端吸积 regime 中基于宽线区的标准标度关系会失效。我们表明一个最小定量实现能在黑洞质量、吸积率和辐射效率范围内重现这种行为。这些结果表明活动星系核发射线现象学由电离辐射场的全局调节而非仅仅由局部气体的存在或条件决定。
英文摘要
Broad emission lines (BELs) are a defining feature of active galactic nuclei (AGNs), yet they weaken or disappear in both very low- and very high-accretion systems. These regimes are typically treated separately, and a unified physical explanation has remained elusive. Here we show that this behavior arises if line formation is governed not by the intrinsic luminosity of the central engine, but by the ionizing radiation field that survives filtering before reaching the broad-line region (BLR). In this picture, line production depends on the product of intrinsic ionizing capability and an effective transmission. Because the former increases from low accretion rates while the latter declines at high accretion rates, the effective ionizing field naturally develops a finite and non-universal window for BEL formation. This framework unifies the absence or extreme faintness of BELs in low-luminosity AGNs, LINERs, and weak-line quasars (WLQs), and accounts for the Baldwin effect and the $R_{\rm Fe}$ trend. It also necessarily implies the breakdown of standard BLR-based scaling relations in extreme accretion regimes. We show that a minimal quantitative realization reproduces this behavior across black-hole mass, accretion rate, and radiative efficiency. These results suggest that AGN emission-line phenomenology is governed by global regulation of the ionizing radiation field rather than by mere presence or condition of local gas.
Comments12 pages, 5 figures, an exploratory preprint
