Extreme MgII Emission in Recently-Quenched Galaxies: A New Sample of Intermediate-Redshift Post-Starburst Quasars from the DESI Early Data Release
Year: 2026
Type: preprint
Abstract: Post-starburst galaxies are galaxies which have recently and rapidly shut off star formation. AGN activity is often invoked to explain this rapid quenching, but most post-starburst selection methods select against optical AGN, motivating searches for "post-starburst quasars." We present DESI observations of ten post-starburst quasars with significant MgII emission ($L_{\text{MgII}} \geq 3 \times 10^{41}$ erg/s). This is the first sample of post-starburst quasars to be selected from a post-starburst galaxy parent sample rather than a quasar catalog. Quasars make up $4.6^{+1.6}_{-1.2}\%$ of the post-starburst parent sample at $0.49 \leq z \leq 1.39$. Using multiwavelength AGN diagnostics, we find that $26^{+3.0}_{-2.8}\%$ of post-starbursts in the parent sample host AGN. We find that post-starburst selection methods are biased against AGN with $\text{L}_{\text{Bol}}\gtrsim10^{45} \textrm{erg s}^{-1}$, potentially removing the quasars responsible for driving outflows that aid in quenching. Finally, we find that 9/10 post-starburst quasars in our sample have no detected broad H$β$, similar to so-called "MgII emitters" that may be the remnants of fading quasars; if confirmed, these objects suggest a link between post-starburst galaxies and variable AGN. Our new sample of post-starburst quasars provides a link between previously reported local and high redshift post-starburst quasars during the epoch when star formation throughout the universe was declining.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Gordon and Betty Moore Foundation, Yale University, Carnegie Institution of Washington, Ohio State University, California Institute of Technology, Harvard University, Johns Hopkins University, New Mexico State University, Space Telescope Science Institute, Flatiron Health, École Polytechnique Fédérale de Lausanne, Eberhard Karls Universität Tübingen, University of Toronto, Max-Planck-Gesellschaft, Ministerio de Ciencia e Innovación, Universität Hamburg, Universidad Nacional Autónoma de México, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Yunnan University, Nanjing University, Rheinische Friedrich-Wilhelms-Universität Bonn, China National Textile and Apparel Council, Leibniz-Institut für Astrophysik Potsdam, Max-Planck-Institut für Astronomie, University of Illinois at Urbana-Champaign, Office of Science, Jet Propulsion Laboratory, University of California, Los Angeles, University of Colorado Boulder, Smithsonian Astrophysical Observatory, Science and Technology Facilities Council, Leibniz-Gemeinschaft, Russian Academy of Sciences, National Astronomical Observatories, Chinese Academy of Sciences, Division of Astronomical Sciences, Lawrence Berkeley National Laboratory
Awards: G1044631029, G1079818582, G1143651532, G1286236842, G1632040200, G1813527838, G1863003419, G4099714421, G419881185, G42916606, G4501827968, G498139845, G5004724115, G5287069595, G6652958823, G6876926712, G7146827954, Management and Operations of the National Optical Astronomy Observatory, G7354628648, The Time Variability and Duty Cycle of Active Galactic Nuclei During Quenching
OpenAlex ID: W7214725752