THE METALLICITY EVOLUTION OF LOW-MASS GALAXIES: NEW CONSTRAINTS AT INTERMEDIATE REDSHIFT

Journal Article · Sat Jun 01 04:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/769/2/148· OSTI ID:22127200

Henry, Alaina; Martin, Crystal L.; Finlator, Kristian ^[1]; Dressler, Alan ^[2]

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1. Department of Physics, University of California, Santa Barbara, CA 93106 (United States)
2. Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

We present abundance measurements from 26 emission-line-selected galaxies at z {approx} 0.6-0.7. By reaching stellar masses as low as 10{sup 8} M{sub Sun }, these observations provide the first measurement of the intermediate-redshift mass-metallicity (MZ) relation below 10{sup 9} M{sub Sun }. For the portion of our sample above M > 10{sup 9} M{sub Sun} (8/26 galaxies), we find good agreement with previous measurements of the intermediate-redshift MZ relation. Compared to the local relation, we measure an evolution that corresponds to a 0.12 dex decrease in oxygen abundances at intermediate redshifts. This result confirms the trend that metallicity evolution becomes more significant toward lower stellar masses, in keeping with a downsizing scenario where low-mass galaxies evolve onto the local MZ relation at later cosmic times. We show that these galaxies follow the local fundamental metallicity relation, where objects with higher specific (mass-normalized) star formation rates (SFRs) have lower metallicities. Furthermore, we show that the galaxies in our sample lie on an extrapolation of the SFR-M{sub *} relation (the star-forming main sequence). Leveraging the MZ relation and star-forming main sequence (and combining our data with higher-mass measurements from the literature), we test models that assume an equilibrium between mass inflow, outflow, and star formation. We find that outflows are required to describe the data. By comparing different outflow prescriptions, we show that momentum, driven winds can describe the MZ relation; however, this model underpredicts the amount of star formation in low-mass galaxies. This disagreement may indicate that preventive feedback from gas heating has been overestimated, or it may signify a more fundamental deviation from the equilibrium assumption.

• OSTI ID: 22127200
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 769; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
EMISSION
EQUILIBRIUM
EVOLUTION
EXTRAPOLATION
FEEDBACK
GALAXIES
HEATING
LIMITING VALUES
MASS
OXYGEN
RED SHIFT
STARS
STELLAR WINDS