随风而逝？$z=0.287$ 类星体宽线区中由时变巴耳末吸收线示踪的潜在气体内流
Gone with the wind? Potential gas inflow in the broad-line region of a QSO at $z=0.287$ traced by time-varying Balmer absorption
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中文总结 AI 辅助
该研究报道了一个红移0.287的类星体，其巴耳末吸收线在10个月内发生显著变化，分解为静止和动态两个分量，推断吸收发生在宽线区，质量内流率与吸积率相当，并伴有X射线弱化，可能代表并合后的活跃吸积阶段。
中文摘要 AI 辅助
我们报告了对来自暗能量光谱仪（DESI）巡天中一个引人注目的类星体 J115724.80-000455.56（红移 $z=0.287$）的光谱观测。该类星体在2021年至2022年间观测参考系中10个月的时间间隔内，其氢巴耳末吸收线表现出变化性。观测到的巴耳末吸收线可分解为两个具有不同运动学特征的分量：一个不变的分量（\"静止\"分量）和一个变化的分量（\"动态\"分量）。两个吸收体的气体柱密度均为 $N_{\rm H}\sim 10^{22}~{\rm cm^{-2}}$，密度可能为 $n_{\rm H}\gtrsim 10^{8}~{\rm cm^{-3}}$。我们推断吸收体的有效物理尺寸很小，约为 $\lesssim 10^{-3}$ pc，这连同时间变化性一起，表明吸收发生在宽线区（BLR）中。两个吸收体的红移后质心速度暗示存在内流，其中推断的质量内流率与该类星体的单历元质量吸积率相当。2022年对该类星体的观测进一步揭示了在2个月内柱密度有10%的变化，表明气体内流可能是持续的。我们还利用爱因斯坦探针（Einstein Probe）获得了新的X射线观测，其揭示的X射线与热光度之比显著低于一般活动星系核（AGN）群体。X射线弱化与强气体遮蔽一致，其柱密度为 $N_{\rm H}= 4.0^{+ 1.6}_{- 1.5}\times10^{23}~{\rm cm^{-2}}$。与光学相比，X射线中观测到的显著更高的气体遮蔽可能表明宽线区内存在暖吸收体，或与光学成像一致的由并合驱动的星系尺度遮蔽增强。因此，该类星体可能代表了近期富气体并合后的一个活跃吸积阶段。
英文摘要
We report spectroscopic observations of a remarkable QSO, J115724.80-000455.56 at $z=0.287$ from the Dark Energy Spectroscopic Instrument (DESI) survey. This QSO exhibits variability in its hydrogen Balmer absorption over a time interval of 10 months in the observed frame between 2021 and 2022. The observed Balmer absorption can be decomposed into two components with distinct kinematics: a non-varying, "stationary" component and a varying, "dynamic" component. Both absorbers have gas column densities of $N_{\rm H}\sim 10^{22}~{\rm cm^{-2}}$ and likely have densities of $n_{\rm H}\gtrsim 10^{8}~{\rm cm^{-3}}$. We inferred small effective physical sizes of $\lesssim 10^{-3}$ pc for the absorbers, which, together with the time variability, suggests that the absorption occurs in the broad-line region (BLR). The reshifted centroid velocities of both absorbers imply an inflow, where the inferred mass inflow rate is comparable to the single-epoch mass accretion rate of this QSO. The 2022 epoch of this QSO further reveals a 10% change in the column density over 2 months, indicating the gas inflow might be continuous. We also obtained new X-ray observations using the $\it Einstein~Probe$, which reveals an X-ray-to-bolometric luminosity ratio significantly below the general AGN population. The X-ray weakness is consistent with strong gas obscuration with $N_{\rm H}= 4.0^{+ 1.6}_{- 1.5}\times10^{23}~{\rm cm^{-2}}$. The substantially higher gas obscuration seen in the X-rays compared to the optical possibly indicates a warm absorber inside the BLR or merger-driven enhancement of the galactic scale obscuration consistent with optical imaging. This QSO might thus represent an active feeding phase after a recent gas-rich merger.
发表机构
- Kavli Institute for Cosmology, University of Cambridge（剑桥大学卡弗里宇宙学研究所）
- Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）
- Centre for Astrophysics Research, University of Hertfordshire（赫特福德大学天体物理学研究中心）
- Institute of Astronomy, University of Cambridge（剑桥大学天体物理研究所）
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