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The Mass-Metallicity Relation in the Faint Infrared Grism Survey

Presentation #120.02 in the session “Emission Lines in Galaxies: Star-formation at Cosmic Noon (Meeting-in-a-Meeting)”.

Published onJun 18, 2021
The Mass-Metallicity Relation in the Faint Infrared Grism Survey

Empirical relations such as the Mass-Metallicity Relation (MZR) and the Fundamental Metallicity Relation (FMR) are important to the ongoing study of galaxy evolution because they correlate the elemental composition of a galaxy’s gas and its stellar mass to a galaxy’s star formation rate (SFR). These relations are well-studied in the low-redshift universe and among high-mass galaxies, but more work is needed to study the interplay of these properties among faint and low-mass sources. In the Faint Infrared Grism Survey, we obtained deep near-infrared spectroscopy of thousands of galaxies from the Hubble Space Telescope’s WFC3 G102 grism instrument. From this sample, we were able to identify ~200 Ha, [OIII], and [OII] strong line emitters in the range 0.3 < z < 2.2, with line fluxes down to 10-17 erg cm-2 s-1 and stellar masses down to 107.7 MSun. For 14 of the emission line galaxies (ELGs), we detected the faint [OIII]4363 emission line in matching VLT/MUSE optical spectra, allowing for the measurement of the gas-phase metallicity via the electron temperature. We measured metallicity for additional ELGs via the R23 method, and constructed a mass-metallicity relation for FIGS galaxies, finding some with substantially lower (7.5 < 12 + log(O/H) < 8.25) metallicity than is more typically found at comparable redshift. We investigated possible correlations and found a link between lower metallicity and increased specific star formation rate (sSFR). We also placed the FIGS galaxies on the FMR, where the low-mass galaxies are outliers even among more modern constructions of the relation. This suggests a need of further study of the emission-line properties of the dwarf galaxy population, both in future missions and with ongoing surveys. The results from FIGS can be compared with ELG results from the HALO7D survey, where Keck/DEIMOS optical spectroscopy was obtained for ~250 ELG’s with Mstar < 109 MSun, providing a broader and uniformly selected sample of low-mass galaxies with which to study the MZR with emission lines.

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