Modeling Star Formation Histories of Changing-Look AGN Host Galaxies with Prospector

Abstract

Changing-look active galactic nuclei, or CL-AGN, are AGN which appear to transition between Seyfert Type 1 and 2 over periods of months to years. Several mechanisms to trigger these transitions have been proposed, but we have yet to conclusively determine their cause. Recent studies suggest CL-AGN are hosted primarily in galaxies which are shutting down star formation (Dodd et al. 2021; Liu et al. 2021, Wang et al. 2023), which may indicate a link between galaxy quenching and changing look events. We use Prospector stellar population synthesis software (Leja et al. 2017; Johnson & Leja 2017; Johnson et al. 2021) to model non-parametric star formation histories for 39 CL-AGN host galaxies. We find that $43_{-12}^{+13}\%$ of our gold sample CL-AGN at z < 0.15 are star forming, while $29_{-10}^{+13}\%$ fall in the Green Valley of the stellar mass-sSFR diagram. At z > 0.15, $57_{-18}^{+13}\%$ of CL-AGN in the gold sample are star-forming and $29_{-14}^{+19}\%$ are in the Green Valley. CL-AGN hosts have similar star formation properties to the host galaxies of Seyfert 1 and 2 AGN at z < 0.15 and to Seyfert 2 AGN at z > 0.15. We find no statistically significant differences in the star formation properties of turn-on and turn-off CL-AGN. We also find no evidence for rapid quenching in the Green Valley CL-AGN. We conclude that CL-AGN state transitions are not associated with the formation history of CL-AGN host galaxies on large spatial scales, implying CL-AGN state transitions may instead result from nuclear-scale or accretion disk effects.

Submitted to ApJ

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• Radio Variability in Recently-Quenched Galaxies: The Impact of TDE or AGN Driven Outflows
• Identifying Changing-Look AGN Transitions in Light Curve Data with the Zwicky Transient Facility