Nuclear Gas Mapping in Extreme Coronal Line Galaxies Exposes Unified Ionization Stratification Across TDE and AGN Regimes

This arXiv preprint (abs/2606.04090, not yet peer-reviewed) compiles optical spectra for a modest sample of 33 ECLEs observed via multi-epoch data from SDSS, DESI and smaller facilities, separating variable/TDE-linked objects from steady AGN-linked ones. The analysis reveals a clear temporal sequence in which [Fe X-XIV] lines appear and fade first, followed by [Fe VII] while [O III] brightens, consistent with either a softening continuum or an outward-moving ionization front after a flare. By assuming virial motion the authors reconstruct radial distances showing coronal-line gas sits between the broad-line and low-ionization narrow-line regions in both variable and non-variable systems, implying similar circumnuclear gas distributions regardless of nuclear activity state. Positive log(distance)–log(M_BH) slopes of 0.63 and 0.69 for [O III] and [Fe VII] align with photoionization scaling rather than pure dynamical expectations. Earlier single-object studies (e.g., Wang et al. 2012 on SDSS J0952) missed this statistical stratification; broader TDE reviews (Gezari 2021) under-emphasized the shared geometry between transient and persistent nuclei. The work therefore supplies rare empirical support for AGN-feedback models in which TDEs illuminate pre-existing gas reservoirs, tightening the observational link between black-hole growth episodes and galaxy co-evolution while highlighting the limits of small-sample virial assumptions and the absence of X-ray or IR constraints.