The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon
We present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲ z ≲ 2.6 ( z _mean = 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass of $\mathrm{log}{({M}_{* }/{M}_{\odot })}_{\mathr...
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acb153 |
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| author | Timothy Gburek Brian Siana Anahita Alavi Najmeh Emami Johan Richard William R. Freeman Daniel P. Stark Christopher Snapp-Kolas |
| author_facet | Timothy Gburek Brian Siana Anahita Alavi Najmeh Emami Johan Richard William R. Freeman Daniel P. Stark Christopher Snapp-Kolas |
| author_sort | Timothy Gburek |
| collection | DOAJ |
| description | We present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲ z ≲ 2.6 ( z _mean = 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass of $\mathrm{log}{({M}_{* }/{M}_{\odot })}_{\mathrm{med}}={8.29}_{-0.43}^{+0.51}$ and a median star formation rate of ${{\rm{S}}{\rm{F}}{\rm{R}}}_{{\rm{H}}\alpha }^{{\rm{m}}{\rm{e}}{\rm{d}}}={2.25}_{-1.26}^{+2.15}\,{M}_{\odot }\,{{\rm{y}}{\rm{r}}}^{-1}$ . We measure the faint electron-temperature-sensitive [O iii ] λ 4363 emission line at 2.5 σ (4.1 σ ) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of $12+\mathrm{log}{({\rm{O}}/{\rm{H}})}_{\mathrm{direct}}={7.88}_{-0.22}^{+0.25}$ ( ${0.15}_{-0.06}^{+0.12}\ {Z}_{\odot }$ ). We investigate the applicability at high z of locally calibrated oxygen-based strong-line metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strong-line ratio. At fixed M _* , our composite is well represented by the z ∼ 2.3 direct-method stellar mass—gas-phase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories $(\mathrm{log}{({M}_{* }/{M}_{\odot })}_{\mathrm{med}}={8.92}_{-0.22}^{+0.31})$ , we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixed M _* and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [O ii ] λ 3729/[O ii ] λ 3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density of ${n}_{e}={1}_{-0}^{+215}\ {\mathrm{cm}}^{-3}$ ( ${n}_{e}={1}_{-0}^{+74}\ {\mathrm{cm}}^{-3}$ ) when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies at z ∼ 2. |
| first_indexed | 2024-03-12T03:24:47Z |
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| last_indexed | 2024-03-12T03:24:47Z |
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| spelling | doaj.art-30b8dfa48ed34e3daf295897b05e60852023-09-03T13:42:31ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01948210810.3847/1538-4357/acb153The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High NoonTimothy Gburek0https://orcid.org/0000-0002-7732-9205Brian Siana1https://orcid.org/0000-0002-4935-9511Anahita Alavi2https://orcid.org/0000-0002-8630-6435Najmeh Emami3https://orcid.org/0000-0003-2047-1689Johan Richard4https://orcid.org/0000-0001-5492-1049William R. Freeman5https://orcid.org/0000-0003-3559-5270Daniel P. Stark6Christopher Snapp-Kolas7https://orcid.org/0000-0002-9593-0053Department of Physics & Astronomy, University of California , Riverside, CA 92521, USA ; timothy.gburek@email.ucr.eduDepartment of Physics & Astronomy, University of California , Riverside, CA 92521, USA ; timothy.gburek@email.ucr.eduIPAC, California Institute of Technology , 1200 E. California Boulevard, Pasadena, CA 91125, USAMinnesota Institute for Astrophysics, University of Minnesota , Minneapolis, MN, 55455, USAUniv Lyon , Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis-Laval, FranceDepartment of Physics & Astronomy, University of California , Riverside, CA 92521, USA ; timothy.gburek@email.ucr.eduSteward Observatory, University of Arizona , 933 N. Cherry Ave, Tucson, AZ 85721, USADepartment of Physics & Astronomy, University of California , Riverside, CA 92521, USA ; timothy.gburek@email.ucr.eduWe present a Keck/MOSFIRE rest-optical composite spectrum of 16 typical gravitationally lensed star-forming dwarf galaxies at 1.7 ≲ z ≲ 2.6 ( z _mean = 2.30), all chosen independent of emission-line strength. These galaxies have a median stellar mass of $\mathrm{log}{({M}_{* }/{M}_{\odot })}_{\mathrm{med}}={8.29}_{-0.43}^{+0.51}$ and a median star formation rate of ${{\rm{S}}{\rm{F}}{\rm{R}}}_{{\rm{H}}\alpha }^{{\rm{m}}{\rm{e}}{\rm{d}}}={2.25}_{-1.26}^{+2.15}\,{M}_{\odot }\,{{\rm{y}}{\rm{r}}}^{-1}$ . We measure the faint electron-temperature-sensitive [O iii ] λ 4363 emission line at 2.5 σ (4.1 σ ) significance when considering a bootstrapped (statistical-only) uncertainty spectrum. This yields a direct-method oxygen abundance of $12+\mathrm{log}{({\rm{O}}/{\rm{H}})}_{\mathrm{direct}}={7.88}_{-0.22}^{+0.25}$ ( ${0.15}_{-0.06}^{+0.12}\ {Z}_{\odot }$ ). We investigate the applicability at high z of locally calibrated oxygen-based strong-line metallicity relations, finding that the local reference calibrations of Bian et al. best reproduce (≲0.12 dex) our composite metallicity at fixed strong-line ratio. At fixed M _* , our composite is well represented by the z ∼ 2.3 direct-method stellar mass—gas-phase metallicity relation (MZR) of Sanders et al. When comparing to predicted MZRs from the IllustrisTNG and FIRE simulations, having recalculated our stellar masses with more realistic nonparametric star formation histories $(\mathrm{log}{({M}_{* }/{M}_{\odot })}_{\mathrm{med}}={8.92}_{-0.22}^{+0.31})$ , we find excellent agreement with the FIRE MZR. Our composite is consistent with no metallicity evolution, at fixed M _* and SFR, of the locally defined fundamental metallicity relation. We measure the doublet ratio [O ii ] λ 3729/[O ii ] λ 3726 = 1.56 ± 0.32 (1.51 ± 0.12) and a corresponding electron density of ${n}_{e}={1}_{-0}^{+215}\ {\mathrm{cm}}^{-3}$ ( ${n}_{e}={1}_{-0}^{+74}\ {\mathrm{cm}}^{-3}$ ) when considering the bootstrapped (statistical-only) error spectrum. This result suggests that lower-mass galaxies have lower densities than higher-mass galaxies at z ∼ 2.https://doi.org/10.3847/1538-4357/acb153Galaxy abundancesDwarf galaxiesHigh-redshift galaxiesGalaxy evolutionInterstellar mediumScaling relations |
| spellingShingle | Timothy Gburek Brian Siana Anahita Alavi Najmeh Emami Johan Richard William R. Freeman Daniel P. Stark Christopher Snapp-Kolas The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon The Astrophysical Journal Galaxy abundances Dwarf galaxies High-redshift galaxies Galaxy evolution Interstellar medium Scaling relations |
| title | The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon |
| title_full | The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon |
| title_fullStr | The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon |
| title_full_unstemmed | The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon |
| title_short | The Direct-method Oxygen Abundance of Typical Dwarf Galaxies at Cosmic High Noon |
| title_sort | direct method oxygen abundance of typical dwarf galaxies at cosmic high noon |
| topic | Galaxy abundances Dwarf galaxies High-redshift galaxies Galaxy evolution Interstellar medium Scaling relations |
| url | https://doi.org/10.3847/1538-4357/acb153 |
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