AI 中文总结
研究27个低红移ECL发射星系的射电性质，通过射电光谱建模发现产生ECL区域团块状且体积填充因子低，与射电发射区域可能不同，为核周介质性质提供探测，是连接星系核多种物理的高能实验室，需多波长监测。
AI 中文摘要
一小部分星系（远小于1%）显示出明亮的、高电离金属发射线，可能是持续的或可变的。这些极端日冕线（ECL）是软X射线光子与致密气体（\(n\gtrsim10^{6 - 7}~{\rm cm^{-3}}\)）相互作用产生的。产生ECL需要高X射线通量，这意味着强烈的核活动，可能源于潮汐破坏事件（TDEs）和活动星系核（AGN）。由于即使在这些类别中ECL也很少见，其产生可能还需要特定环境条件，但细节尚不清楚。本文展示了27个低红移（\(z<0.3\)）ECL发射星系（ECLEs）的射电性质，为这些系统中核周介质（CNM；距离黑洞\(\lesssim1\) pc）的性质提供了独特且前所未有的探测。发现约50%的ECLEs产生射电同步辐射，其光度和演化与TDEs和/或AGN一致。对四个ECLEs的射电光谱建模表明，产生ECL的区域（1）是团块状的，体积填充因子低（\(10^{-5}\lesssim f_{V}\lesssim10^{-2}\)），（2）可能与射电发射区域不同。对于随时间变化的ECLEs，这些是对以前静止星系核中CNM几何形状的一些首次观测限制。ECLEs的独特性质使其成为连接星系核中吸积、光电离和反馈物理的优秀高能实验室，因此需要持续的多波长监测。
英文摘要
A tiny fraction ($\ll1\%$) of galaxies display luminous, high-ionization metal emission lines, which may be persistent or variable. These extreme coronal lines (ECLs) are produced when soft X-ray photons intercept dense gas ($n\gtrsim10^{6-7}~{\rm cm^{-3}}$). The high X-ray flux required implicates intense nuclear activity, likely originating from tidal disruption events (TDEs) and active galactic nuclei (AGN). As ECLs are rarely seen even within these classes, their production may also require specific environmental conditions, but the details remain unclear (e.g., the geometry and volume filling factor of the ECL-producing gas). Here, we present the radio properties of a population of $27$ low-redshift ($z<0.3$) ECL emitting galaxies (ECLEs), providing a unique and previously unexplored probe of the properties of the circumnuclear medium (CNM; $\lesssim1$ pc from the black hole) in these systems. We find that $\sim 50\%$ of ECLEs produce radio synchrotron emission with luminosity and evolution consistent with TDEs and/or AGN. Radio spectral modeling of four ECLEs reveals that the ECL-producing region is (1) clumpy with a low volume filling factor ($10^{-5}\lesssim f_{V}\lesssim10^{-2}$) and (2) likely distinct from the radio emitting region (implying, e.g., a clumpy toroidal geometry). For time-variable ECLEs, these are some of the first observational constraints on the CNM geometry in formerly quiescent galactic nuclei. The unique nature of ECLEs makes them an excellent high-energy laboratory to connect the physics of accretion, photoionization, and feedback in galactic nuclei, thus motivating continued multi-wavelength monitoring.
Comments24 pages, 5 figures. Submitted to ApJ. Comments welcome
