Mapping the nuclear environments of extreme coronal line emitting galaxies
Abstract
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.
// Source
Authors: Daniel Kynoch, Or Graur, Peter Clark, J. A. Olmos Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, P. Doel, J. E. Forero-Romero, S. Gontcho A Gontcho, G. Gutierrez, R. Joyce, S. Juneau, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, J. Moustakas, S. Panda, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, E. Sanchez, D. Schlegel, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou, H. Zou
Institutions: Universidad Nacional Autónoma de México, University of Virginia, University of Michigan, Boston University, University College London, Universidad Complutense de Madrid, Sorbonne Université, Centre National de la Recherche Scientifique, University of Waterloo, Institució Catalana de Recerca i Estudis Avançats, Universitat Politècnica de Catalunya, University of Southampton, University of Milan, University of Portsmouth, Sejong University, National Astronomical Observatories, Lawrence Berkeley National Laboratory, Fermi National Accelerator Laboratory, American Museum of Natural History, Community Science and Data Center, NSF NOIRLab, Instituto de Astrofísica de Andalucía, Gemini South Observatory, Institut National de Physique Nucléaire et de Physique des Particules, Istituto Nazionale di Fisica Nucleare, Sezione di Milano, Universidad de Los Andes, Universidad de Los Andes, State Street (United States), Brera Astronomical Observatory, Institute for High Energy Physics, Perimeter Institute, Laboratoire de Physique Nucléaire et de Hautes Énergies, Siena College