Molecular Gas Reservoirs in Massive Quiescent Galaxies at z ∼ 0.7 Linked to Late-time Star Formation
Abstract

We explore how the presence of detectable molecular gas depends on the inferred star formation histories (SFHs) in eight massive, quiescent galaxies atz∼ 0.7. Half of the sample have clear detections of molecular gas, traced by CO(2–1). We find that the molecular gas content is unrelated to the rate of star formation decline prior to the most recent 1 Gyr, suggesting that the gas reservoirs are not left over from their primary star formation epoch. However, the recent SFHs of CO-detected galaxies demonstrate evidence for secondary bursts of star formation in their last Gyr. The fraction of stellar mass formed in these secondary bursts ranges fromfburst≈ 0.3%–6% and ended betweentend-burst≈ 0–330 Myr ago. The CO-detected galaxies form a higher fraction of mass in the last Gyr ($fM1Gyr=2.6%±1.8%$) compared to the CO-undetected galaxies ($fM1Gyr=0.2%±0.1%$). The galaxies with gas reservoirs have enhanced late-time star formation, highlighting this as a contributing factor to the observed heterogeneity in the gas reservoirs in high-redshift quiescent galaxies. We find that the amount of gas and star formation driven by these secondary bursts are inconsistent with that expected from dry minor mergers, and instead are likely driven by more »

Authors:
; ; ; ; ; ; ; ;
Publication Date:
NSF-PAR ID:
10380856
Journal Name:
The Astrophysical Journal
Volume:
940
Issue:
1
Page Range or eLocation-ID:
Article No. 39
ISSN:
0004-637X
Publisher:
DOI PREFIX: 10.3847
National Science Foundation
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