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Metal-Poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship Between Stellar Mass, Temperature-Based Metallicity, and Star Formation RateWe report on the discovery of 28 redshift (z) approximately equal to 0.8 metal-poor galaxies in DEEP2. These galaxies were selected for their detection of the weak [O (sub III)] lambda 4363 emission line, which provides a "direct" measure of the gas-phase metallicity. A primary goal for identifying these rare galaxies is to examine whether the fundamental metallicity relation (FMR) between stellar mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass and high SFR galaxies. The FMR suggests that higher SFR galaxies have lower metallicity (at fixed stellar mass). To test this trend, we combine spectroscopic measurements of metallicity and dust-corrected SFR with stellar mass estimates from modeling the optical photometry. We find that these galaxies are 1.05 plus or minus 0.61 dex above the redshift (z) approximately 1 stellar mass-SFR relation and 0.23 plus or minus 0.23 dex below the local mass-metallicity relation. Relative to the FMR, the latter offset is reduced to 0.01 dex, but significant dispersion remains dex with 0.16 dex due to measurement uncertainties). This dispersion suggests that gas accretion, star formation, and chemical enrichment have not reached equilibrium in these galaxies. This is evident by their short stellar mass doubling timescale of approximately equal to 100 (sup plus 310) (sub minus 75) million years which suggests stochastic star formation. Combining our sample with other redshift (z) of approximately 1 metal-poor galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar mass) that is significant at 94.4 percent confidence. We interpret this positive correlation as recent star formation that has enriched the gas but has not had time to drive the metal-enriched gas out with feedback mechanisms.
Document ID
20160011264
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Ly, Chun
(Universities Space Research Association Greenbelt, MD, United States)
Rigby, Jane R.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Cooper, Michael
(California Univ. Irvine, CA, United States)
Yan, Renbin
(Kentucky Univ. Lexington, KY, United States)
Date Acquired
September 15, 2016
Publication Date
May 19, 2015
Publication Information
Publication: The Astrophysical Journal
Publisher: The Astrophysical Journal
Volume: 805
Issue: 1
e-ISSN: 1538-4357
Subject Category
Astronomy
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN35428
Funding Number(s)
CONTRACT_GRANT: NNH15CO48B
CONTRACT_GRANT: NNG04GC89G
Distribution Limits
Public
Copyright
Other
Keywords
Metal-Poor
Strongly
Star-Forming

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