Photometric variability in star-forming galaxies as evidence for low-mass AGN and a precursor to quenching

Journal Article · Wed Aug 10 00:00:00 UTC 2022 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stac2188 · OSTI ID:1982649

Cleland, Cressida ^[1]; McGee, Sean L. ^[1]

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1. University of Birmingham (United Kingdom)

We measure the optical variability in ~16 500 low-redshift (z ~ 0.1) galaxies to map the relations between active galactic nucleus (AGN) activity and galaxy stellar mass, specific star formation rate, half-light radius, and bulge-to-total ratio. To do this, we use a reduced χ² variability measure on >10 epoch light curves from the Zwicky Transient Facility and combine with spectroscopic data and derive galaxy parameters from the Sloan Digital Sky Survey. We find that below the stellar mass of 10¹¹ M_⊙, galaxies classed as star-forming via the Baldwin–Phillips–Terlevich diagram have higher mean variabilities than AGN or composite galaxies. Revealingly, the highest mean variabilities occur in star-forming galaxies in a narrow range of specific star formation rate: -11 < log(sSFR/yr^-1) < -10. In very actively star-forming galaxies [log(sSFR/yr^-1) > -10], the reduced variability implies a lack of instantaneous correlation with star formation rate. Our results may indicate that a high level of variability, and thus black hole growth, acts as a precursor for reduced star formation, bulge growth, and revealed AGN-like emission lines. These results add to the mounting evidence that optical variability can act as a viable tracer for low-mass AGNs and that such AGNs can strongly affect their host galaxy.

• Research Organization: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS); University of Birmingham (United Kingdom)
• Sponsoring Organization: Alfred P. Sloan Foundation; Higher Education Funding Council for England; Japanese Monbukagakusho; Max Planck Society; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Science and Technology Facilities Council; USDOE Office of Science (SC)
• OSTI ID: 1982649
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 4 Vol. 515; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United States
• Language: English