TeV Emission in NGC 4278: Shock Energetics Insufficient, Compact Origin Favored

Abstract The Large High Altitude Air Shower Observatory recently detected TeV emission from the low-luminosity active galactic nucleus (LLAGN) NGC 4278. Integral-field spectroscopy with MEGARA revealed ionized outflows on hundred-parsec scales with kinetic power E ˙ shock ∼ 1 0 38 erg s −1 , well below the TeV luminosity L γ ≳ 10 41 erg s −1 . The implied efficiencies, η ≳ 1000, are far above unity, showing that shocks cannot account for the TeV emission. Contemporaneous Fermi-Large Area Telescope and Swift data, consistent with a compact synchrotron self-Compton jet component, favor a nuclear origin. NGC 4278 is the first low-ionization nuclear emission-line region (LINER)/LLAGN of its class detected at TeV energies, a benchmark for LINERs with outflows and a prime target for the Cherenkov Telescope Array Observatory. I conclude that the TeV photons arise from a compact nuclear accelerator, while optical outflows trace larger-scale jet–ISM interactions that coexist but do not power the TeV radiation.