揭示鲍德温效应的物理驱动因素：宽线区中的气体密度
Revealing the Physical Driver of the Baldwin Effect: Gas Density in the Broad-Line Region
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中文总结 AI 辅助
本研究以41159个射电类星体为样本，发现鲍德温效应斜率与爱丁顿比正相关，宽线区气体密度是其主要物理驱动因素，为AGN吸积状态及耦合演化提供了物理框架。
中文摘要 AI 辅助
鲍德温效应——活动星系核（AGN）中发射线的等效宽度与连续谱光度之间的反相关关系——已被知晓近五十年，但其物理起源仍知之甚少。利用从斯隆数字巡天和低频阵列两米天空巡天构建的包含41159个射电类星体的样本，我们研究了射电宁静（RQ）和射电噪（RL）类星体中MgII宽发射线鲍德温效应的起源及潜在物理机制。我们发现，在两类样本中，鲍德温效应的斜率β与爱丁顿比λ_Edd呈正相关，且在固定λ_Edd下，RL类星体的β比RQ类星体更陡。光电离模拟显示，β主要由宽线区（BLR）的气体密度决定：气体密度越低，斜率越陡。这种由密度驱动的机制自然将鲍德温效应与更广泛的AGN演化背景联系起来。具体而言，更高的λ_Edd会驱动更强的吸积盘风，导致BLR更致密、β更平缓。我们的研究结果表明，BLR气体密度是“全局”鲍德温效应的主要物理驱动因素，为解释AGN吸积状态及其与寄主星系的耦合演化提供了物理基础框架。
英文摘要
The Baldwin effect --- the inverse correlation between the equivalent width of emission lines and the continuum luminosity in active galactic nuclei (AGNs) --- has been known for nearly five decades, yet its physical origin remains poorly understood. Using a sample of 41,159 radio quasars constructed from the Sloan Digital Sky Survey and the Low-Frequency Array Two-metre Sky Survey, we investigate the origin and underlying physics of the Baldwin effect of MgII broad emission lines in both radio-quiet (RQ) and radio-loud (RL) quasars. We find that the slope $β$ of the Baldwin effect is positively correlated with the Eddington ratio $λ_{\rm Edd}$ in both populations, and RL quasars exhibit steeper $β$ than their RQ quasars at fixed $λ_{\rm Edd}$. Photoionization simulations reveal that the $β$ is primarily governed by the gas density in the broad-line region (BLR): lower gas densities yield steeper slopes. This density-driven mechanism naturally connects the Baldwin effect to the broader AGN evolutionary context. Specifically, higher $λ_{\rm Edd}$ drive stronger accretion disk winds, leading to denser BLRs and shallower $β$. Our findings indicate that BLR gas density serves as the primary physical driver underlying the "global" Baldwin effect, offering a physically grounded framework for interpreting AGN accretion states and their coupled evolution with host galaxies.
