Mapping the nuclear environments of extreme coronal line emitting galaxies
Abstract
Extreme coronal line emitters (ECLEs) are a rare class of galactic nuclei exhibiting unusually strong high-ionisation forbidden emission lines, and several ECLEs have been linked to tidal disruption events (TDEs). In this work, we compile and analyse optical spectra of 33 ECLEs, dividing them into variable, TDE-linked sources and non-variable, AGN-linked systems. Using multi-epoch spectroscopy from the Sloan Digital Sky Survey, Dark Energy Spectroscopic Instrument, and other facilities, we investigate the evolution of the emission line spectra and measure emission line profiles. Many variable ECLEs have changing spectra in which the highest-ionisation lines (e.g., [Fe X]-[Fe XIV]) appear and fade first, followed by [Fe VII], accompanied by brightening of [O III]. These changes may reflect a softening ionising continuum, the outward propagation of the ionisation front following the TDE flare, or both. Assuming virial motion, we translate line widths into characteristic radial distances, reconstructing the spatial distribution of line-emitting gas. Coronal lines are generally emitted at radii intermediate between the broad line region and the low-ionisation narrow line region. This ionisation stratification is seen in many sources, with similar incidence in variable and non-variable ECLEs, suggesting no apparent difference in circumnuclear gas distributions between active and quiescent nuclei. We find positive correlations between gas distance and black hole mass for both [O III] and [Fe VII]: the log(Distance)-log(Mass) relations have slopes 0.63±0.08 and 0.69±0.12, respectively, broadly consistent with a Mass0.5 dependence and with characteristic radii set primarily by photoionisation.
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BibTeX
@misc{kynoch2026mapping,
title = {{Mapping the nuclear environments of extreme coronal line emitting galaxies}},
author = {Daniel Kynoch and Or Graur and Peter Clark and J. N. Aguilar and S. Ahlen and D. Bianchi and D. Brooks and T. Claybaugh and A. de la Macorra and P. Doel and J. E. Forero-Romero and S. Gontcho A Gontcho and G. Gutierrez and R. Joyce and S. Juneau and M. Landriau and L. Le Guillou and A. Meisner and R. Miquel and J. Moustakas and S. Panda and W. J. Percival and F. Prada and I. Pérez-Ràfols and G. Rossi and E. Sanchez and D. Schlegel and J. Silber and D. Sprayberry and G. Tarlé and B. A. Weaver and R. Zhou and H. Zou},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2606.04090},
eprint = {2606.04090},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.04090},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Mapping the nuclear environments of extreme coronal line emitting galaxies
AU - Daniel Kynoch
AU - Or Graur
AU - Peter Clark
AU - J. N. Aguilar
AU - S. Ahlen
AU - D. Bianchi
AU - D. Brooks
AU - T. Claybaugh
AU - A. de la Macorra
AU - P. Doel
AU - J. E. Forero-Romero
AU - S. Gontcho A Gontcho
AU - G. Gutierrez
AU - R. Joyce
AU - S. Juneau
AU - M. Landriau
AU - L. Le Guillou
AU - A. Meisner
AU - R. Miquel
AU - J. Moustakas
AU - S. Panda
AU - W. J. Percival
AU - F. Prada
AU - I. Pérez-Ràfols
AU - G. Rossi
AU - E. Sanchez
AU - D. Schlegel
AU - J. Silber
AU - D. Sprayberry
AU - G. Tarlé
AU - B. A. Weaver
AU - R. Zhou
AU - H. Zou
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2606.04090
UR - https://arxiv.org/abs/2606.04090
AB - Extreme coronal line emitters (ECLEs) are a rare class of galactic nuclei exhibiting unusually strong high-ionisation forbidden emission lines, and several ECLEs have been linked to tidal disruption events (TDEs). In this work, we compile and analyse optical spectra of 33 ECLEs, dividing them into variable, TDE-linked sources and non-variable, AGN-linked systems. Using multi-epoch spectroscopy from the Sloan Digital Sky Survey, Dark Energy Spectroscopic Instrument, and other facilities, we investigate the evolution of the emission line spectra and measure emission line profiles. Many variable ECLEs have changing spectra in which the highest-ionisation lines (e.g., [Fe X]-[Fe XIV]) appear and fade first, followed by [Fe VII], accompanied by brightening of [O III]. These changes may reflect a softening ionising continuum, the outward propagation of the ionisation front following the TDE flare, or both. Assuming virial motion, we translate line widths into characteristic radial distances, reconstructing the spatial distribution of line-emitting gas. Coronal lines are generally emitted at radii intermediate between the broad line region and the low-ionisation narrow line region. This ionisation stratification is seen in many sources, with similar incidence in variable and non-variable ECLEs, suggesting no apparent difference in circumnuclear gas distributions between active and quiescent nuclei. We find positive correlations between gas distance and black hole mass for both [O III] and [Fe VII]: the log(Distance)-log(Mass) relations have slopes 0.63±0.08 and 0.69±0.12, respectively, broadly consistent with a Mass^0.5 dependence and with characteristic radii set primarily by photoionisation.
ER -