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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
CO Emission, Molecular Gas, and Metallicity in Main-sequence Star-forming Galaxies at z ∼ 2.3
Astrophysical Journal, Volume 942, No. 1, Article 24, Year 2023
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Description
We present observations of CO(3−2) in 13 main-sequence z = 2.0-2.5 star-forming galaxies at log ( M * / M ⊙ ) = 10.2 - 10.6 that span a wide range in metallicity (O/H) based on rest-optical spectroscopy. We find that L CO ( 3 − 2 ) ′ /SFR decreases with decreasing metallicity, implying that the CO luminosity per unit gas mass is lower in low-metallicity galaxies at z ∼ 2. We constrain the CO-to-H2 conversion factor (α CO) and find that α CO inversely correlates with metallicity at z ∼ 2. We derive molecular gas masses (M mol) and characterize the relations among M *, SFR, M mol, and metallicity. At z ∼ 2, M mol increases and the molecular gas fraction (M mol/M *) decreases with increasing M *, with a significant secondary dependence on SFR. Galaxies at z ∼ 2 lie on a near-linear molecular KS law that is well-described by a constant depletion time of 700 Myr. We find that the scatter about the mean SFR−M *, O/H−M *, and M mol−M * relations is correlated such that, at fixed M *, z ∼ 2 galaxies with larger M mol have higher SFR and lower O/H. We thus confirm the existence of a fundamental metallicity relation at z ∼ 2, where O/H is inversely correlated with both SFR and M mol at fixed M *. These results suggest that the scatter of the z ∼ 2 star-forming main sequence, mass-metallicity relation, and M mol-M * relation are primarily driven by stochastic variations in gas inflow rates. We place constraints on the mass loading of galactic outflows and perform a metal budget analysis, finding that massive z ∼ 2 star-forming galaxies retain only 30% of metals produced, implying that a large mass of metals resides in the circumgalactic medium. © 2023. The Author(s). Published by the American Astronomical Society.
Authors & Co-Authors
Sanders, Ryan L.
United States, Davis
University of California, Davis
Shapley, Alice E.
United States, Los Angeles
University of California, Los Angeles
Shivaei, Irene
United States, Tucson
The University of Arizona
Popping, Gergö
Germany, Garching Bei Munchen
European Southern Observatory
Reddy, Naveen A.
United States, Riverside
University of California, Riverside
Dav́e, Romeel
United Kingdom, Edinburgh
The University of Edinburgh
Price, Sedona H.
Germany, Garching Bei Munchen
Max Planck Institute for Extraterrestrial Physics
Mobasher, Bahram
United States, Riverside
University of California, Riverside
Kriek, Mariska T.
Netherlands, Leiden
Universiteit Leiden
Coil, Alison L.
United States, La Jolla
University of California, San Diego
Siana, Brian D.
United States, Riverside
University of California, Riverside
Statistics
Citations: 9
Authors: 11
Affiliations: 9
Identifiers
Doi:
10.3847/1538-4357/aca46f
ISSN:
0004637X
Research Areas
Environmental