Exploring the Link between Extreme Coronal Line Emitters and Tidal Disruption Events

Abstract

Galaxies with minimal or no activity from their nucleus can still exhibit significant coronal line (CL) emission, often exceeding the strength of typical narrow emission lines. Many of these CLs require ionization potentials of ≥100 eV, implying the need for intense extreme-ultraviolet and/or soft X-ray flux. Tidal disruption events (TDEs) produced by black holes at galaxy centers are expected to generate such emission lines, yet this link remains underexplored. To evaluate whether CLs are reliable tracers of TDEs, we identified a sample of optical CL galaxies from the Early Data Release of the Dark Energy Spectroscopic Instrument. Our analysis reveals 84 galaxies displaying coronal emission lines among 1.8 million unique targets. Nine sources lie in the active galactic nuclei (AGNs)–starburst composite region and may be AGN-related, so their connection to TDEs remains uncertain. We identified 11 galaxies with spectroscopic coverage in the Sloan Digital Sky Survey, but only 1 exhibits detectable CL variability. We examined the color–magnitude relationship of these extreme coronal line emitters (ECLEs) and found that most are located in the green valley, similar to TDEs. Additionally, our comparison of ECLEs with known TDEs indicates that the stellar mass and star formation rates of ECLE hosts are largely consistent with those of TDE hosts, with many ECLEs also residing within the green valley.

Keywords

• Tidal disruption
• Emission line galaxies