ALMA Measures Rapidly Depleted Molecular Gas Reservoirs in Massive Quiescent Galaxies at z ∼ 1.5

• Published in: The Astrophysical journal 2021-02, Vol.908 (1), p.54
• Main Authors: Williams, Christina C., Spilker, Justin S., Whitaker, Katherine E., Davé, Romeel, Woodrum, Charity, Brammer, Gabriel, Bezanson, Rachel, Narayanan, Desika, Weiner, Benjamin
• Format: Article
• Language: English
• Subjects: Astronomical models; Astrophysics; Carbon monoxide; CO line emission; Compact galaxies; Critical mass; Dark matter; Depletion; Deposition; Early-type galaxies; Empirical analysis; Galactic halos; Galaxies; Galaxy evolution; Galaxy formation; Galaxy quenching; Halos; High-redshift galaxies; Molecular gas; Molecular gases; Quenched galaxies; Radio telescopes; Reservoirs; Spectroscopy; Star & galaxy formation; Star formation; Star formation rate; Stars & galaxies; Stellar mass
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/abcbf6

We present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) spectroscopy of six massive (log 10 / > 11.3) quiescent galaxies at z  ∼ 1.5. These data represent the largest sample using CO emission to trace molecular gas in quiescent galaxies above z  > 1, achieving an average 3 σ sensitivity of ∼ 10 10 . We detect one galaxy at 4 σ significance and place upper limits on the molecular gas reservoirs of the other five, finding molecular gas mass fractions (3 σ upper limits). This is 1–2 orders of magnitude lower than coeval star-forming galaxies at similar stellar mass, and comparable to galaxies at z  = 0 with similarly low specific star formation rate (sSFR). This indicates that their molecular gas reservoirs were rapidly and efficiently used up or destroyed, and that gas fractions are uniformly low (