Detailed Accretion History of the Supermassive Black Hole in NGC 5972 over the Past ≳104 yr through the Extended Emission-line Region

We present integral field spectroscopic observations of NGC 5972 obtained with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope. NGC 5972 is a nearby galaxy containing both an active galactic nucleus (AGN) and an extended emission-line region (EELR) reaching out to ∼17 kpc from the...

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Bibliographic Details
Published in:The Astrophysical journal 2022-09, Vol.936 (1), p.88
Main Authors: Finlez, C., Treister, E., Bauer, F., Keel, W., Koss, M., Nagar, N., Sartori, L., Maksym, W. P., Venturi, G., Tubín, D., Harvey, T.
Format: Article
Language:English
Subjects:
Accretion
Active galactic nuclei
AGN host galaxies
Astrophysics
Black holes
Deposition
Emissions
Galaxies
Ionization
Kinematics
Luminosity
Photoionization
Quasars
Rotating disks
Seyfert galaxies
Spectroscopic observation
Spectroscopy
Supermassive black holes
Travel time
Very Large Telescope
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Summary:We present integral field spectroscopic observations of NGC 5972 obtained with the Multi-Unit Spectroscopic Explorer at the Very Large Telescope. NGC 5972 is a nearby galaxy containing both an active galactic nucleus (AGN) and an extended emission-line region (EELR) reaching out to ∼17 kpc from the nucleus. We analyze the physical conditions of the EELR using spatially resolved spectra, focusing on the radial dependence of ionization state together with the light-travel time distance to probe the variability of the AGN on ≳104 yr timescales. The kinematic analysis suggests multiple components: (a) a faint component following the rotation of the large-scale disk, (b) a component associated with the EELR suggestive of extraplanar gas connected to tidal tails, and (c) a kinematically decoupled nuclear disk. Both the kinematics and the observed tidal tails suggest a major past interaction event. Emission-line diagnostics along the EELR arms typically evidence Seyfert-like emission, implying that the EELR was primarily ionized by the AGN. We generate a set of photoionization models and fit these to different regions along the EELR. This allows us to estimate the bolometric luminosity required at different radii to excite the gas to the observed state. Our results suggest that NGC 5972 is a fading quasar, showing a steady gradual decrease in intrinsic AGN luminosity, and hence the accretion rate onto the SMBH, by a factor ∼100 over the past 5 × 104 yr.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac854e