SQuIGG L → E: Buried Star Formation Cannot Explain the Rapidly Fading CO(2–1) Luminosity in Massive, z ∼ 0.7 Post-starburst Galaxies

The Astronomical Journal, vol. 170, pp. 351

Abstract

Abstract Observational and theoretical studies have long held that rapid gas consumption in starbursts is responsible for the formation of the most massive quiescent galaxies at high redshift. However, studies of recently quenched “post-starburst” galaxies have discovered that a number of them are surprisingly luminous in CO, challenging this assumption. We present deep Atacama Large Millimeter/submillimeter Array CO(2–1) observations of 50 massive ( log ( M ⋆ / M ⊙ ) ∼ 11.2 ) post-starburst galaxies from the SQuIGG L → E sample at z ∼ 0.7. We detect a large fraction (27/50) of the galaxies in CO(2–1). We perform new spectral energy distribution (SED) fits incorporating mid- and far-IR photometry to measure the star formation rates (SFRs) and histories that can reproduce both the rest-optical and dust properties of these galaxies. We find that the CO luminosity correlates with the age of the recent starburst, suggesting a gas-removal timescale of ≲150 Myr, an order of magnitude shorter than is implied by their SFRs under standard birth cloud dust assumptions. We find that while allowing for significantly more attenuation in birth clouds can raise SFRs by ∼0.5 dex, for almost all galaxies, it is neither required to fit the observed IR SED, nor is it sufficient to explain the observed depletion trend. Even the combination of significant buried star formation and ULIRG-like α CO is not enough to explain this decay in CO luminosity. Furthermore, there is no strong evidence to support either of those modifications to the depletion time. Therefore, it remains a distinct possibility that the age–CO luminosity trend should not be interpreted as an evolutionary sequence, and that gas-rich SQuIGG L → E galaxies will soon rejuvenate.

Authors 15

1. David J. Setton corresponding

   Princeton University

   Affiliation as printed

   Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA

2. Justin S. Spilker corresponding

   Texas A&M University

   Affiliation as printed

   Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX 77843-4242, USA

3. Rachel Bezanson corresponding

   University of Pittsburgh

   Affiliation as printed

   Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA

4. Katherine A. Suess corresponding

   University of Colorado Boulder

   Affiliation as printed

   Department for Astrophysical & Planetary Science, University of Colorado, Boulder, CO 80309, USA

5. Jenny E. Greene corresponding

   Princeton University

   Affiliation as printed

   Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA

6. Andy D. Goulding corresponding

   Princeton University

   Affiliation as printed

   Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA

7. Elia Cenci corresponding

   University of Geneva · University of Zurich

   Affiliation as printed

   Department of Astronomy, University of Geneva, Chemin Pegasi 51, Versoix CH-1290, Switzerland

   Department of Astrophysics, Universität Zürich, Winterthurerstrasse 190, Zurich CH-8057, Switzerland

8. Vincenzo R. D’Onofrio corresponding

   Texas A&M University

   Affiliation as printed

   Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX 77843-4242, USA

9. ROBERT J. FELDMANN corresponding

   University of Zurich

   Affiliation as printed

   Department of Astrophysics, Universität Zürich, Winterthurerstrasse 190, Zurich CH-8057, Switzerland

10. Mariska Kriek corresponding Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands

11. Anika Kumar corresponding

    Rochester Institute of Technology · University of Pittsburgh

    Affiliation as printed

    Department of Physics and Astronomy and PITT PACC, University of Pittsburgh, Pittsburgh, PA 15260, USA

    Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623, USA

12. Yuanze Luo corresponding

    Texas A&M University

    Affiliation as printed

    Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX 77843-4242, USA

13. Desika Narayanan corresponding

    University of Florida

    Affiliation as printed

    Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611, USA

14. Margaret E. Verrico corresponding

    University of Illinois Urbana-Champaign · National Center for Supercomputing Applications

    Affiliation as printed

    Center for AstroPhysical Surveys, National Center for Supercomputing Applications, 1205 West Clark Street, Urbana, IL 61801, USA

    University of Illinois Urbana-Champaign Department of Astronomy, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA

15. Pengpei Zhu corresponding

    DTU Space · Technical University of Denmark

    Affiliation as printed

    Cosmic Dawn Center (DAWN), Denmark

    DTU Space, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark