Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

Sanders, Ryan L.; Shapley, Alice E.; Zhang, Kai; Yan, Renbin

doi:10.3847/1538-4357/aa93e4

Cited by 98 publications

(152 citation statements)

References 106 publications

(263 reference statements)

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“…The M * -binned z ∼ 0 SDSS stacks of Andrews & Martini (2013) are shown as gray squares in the left panel of Figure 4. The open squares show the values derived by Andrews & Martini (2013), while the filled squares denote the derived metallicities after correcting for contamination from diffuse ionized gas according to Sanders et al (2017), shifted ∼ 0.05 dex lower in O/H. The orange line shows the best-fit MZR to a sample of z ∼ 0.8 galaxies with [O iii]λ4363 detections from Ly et al (2016).…”

Section: The Direct-methods Z ∼ 22 Mass-metallicity Relationmentioning

confidence: 99%

“…The 1σ confidence bounds are taken from 68th percentile width of the resulting distribution. We compare the z > 1 sample and medians to low-and intermediate-redshift samples to investigate potential evolution: individual z = 0 H ii regions (black line; Pilyugin & Grebel 2016;Sanders et al 2017), z ∼ 0 star-forming galaxies from the Sloan Digital Sky Survey (SDSS, gray points; Izotov et al 2006), and z ∼ 0.8 star-forming galaxies from DEEP2 (orange points; Jones et al 2015). The oxygen abundances of each sample have been recalculated using our methodology.…”

Section: Metallicity Calibrations At Z >mentioning

confidence: 99%

“…(e.g.,Salim et al 2015;Davé et al 2017;Kashino et al 2017;Sanders et al 2018). Using theAndrews & Martini (2013) z ∼ 0 SDSS stacks binned in M * +SFR and corrected for diffuse ionized gas(Sanders et al 2017), we fit ∆log(O/H) vs. ∆log(SFR) using direct-method metallicities (gray points and black dashed line in…”

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confidence: 99%

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The MOSDEF survey: direct-method metallicities and ISM conditions at z ∼ 1.5–3.5

Sanders

Shapley

Reddy

et al. 2019

Monthly Notices of the Royal Astronomical Society

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185

288

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We present detections of [O iii]λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7 − 3.6. We combine new measurements from the MOSFIRE Deep Evolution Field (MOSDEF) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(O/H) < 8.2 and log(M * /M ) = 7 − 10. We find that strong-line calibrations based on local analogs of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. We construct the first mass-metallicity relation at z > 1 based purely on direct-method O/H, finding a slope that is consistent with strong-line results. Directmethod O/H evolves by 0.1 dex at fixed M * and SFR from z ∼ 0 − 2.2. We employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. Stellar models with super-solar O/Fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. We find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and O/H, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. These results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by super-solar O/Fe values at high redshift caused by rapid formation timescales. Given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼ 10 10 M are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization.

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Section: The Direct-methods Z ∼ 22 Mass-metallicity Relationmentioning

confidence: 99%

Section: Metallicity Calibrations At Z >mentioning

confidence: 99%

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The MOSDEF survey: direct-method metallicities and ISM conditions at z ∼ 1.5–3.5

Sanders

Shapley

Reddy

et al. 2019

Monthly Notices of the Royal Astronomical Society

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185

288

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“…Although affected by a certain number of weaknesses, mainly attributed to the presence of temperature and chemical inhomogeneities in the nebulae (Peimbert 1967;Stasińska 2002Stasińska , 2005 and/or to the contribution of diffuse gas to line emission when dealing with global galaxy spectra (Sanders et al 2017;Zhang et al 2017), the metallicity measurements based on the T e method have proven to be in better agreement with independent measurements of stellar metallicities performed in young (i.e. < 10 Myr) stars (see e.g.…”

Section: Introductionmentioning

confidence: 98%

The mass–metallicity and the fundamental metallicity relation revisited on a fully Te-based abundance scale for galaxies

Curti

Mannucci

Cresci

et al. 2019

Monthly Notices of the Royal Astronomical Society

277

472

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The relationships between stellar mass, gas-phase metallicity and star formation rate (i.e. the Mass-Metallicity, MZR, and the Fundamental Metallcity Relation, FMR) in the local Universe are revisited by fully anchoring the metallicity determination for SDSS galaxies on the T e abundance scale defined exploiting the strong-line metallicity calibrations presented in Curti et al. (2017). Self-consistent metallicity measurements allow a more unbiased assessment of the scaling relations involving M, Z and SFR, which provide powerful constraints for the chemical evolution models. We parametrise the MZR with a new functional form which allows us to better characterise the turnover mass. The slope and saturation metallicity are in good agreement with previous determinations of the MZR based on the Te method, while showing significantly lower normalisation compared to those based on photoionisation models. The Z-SFR dependence at fixed stellar mass is also investigated, being particularly evident for highly star forming galaxies, where the scatter in metallicity is reduced up to a factor of ∼ 30%. A new parametrisation of the FMR is given by explicitly introducing the SFR-dependence of the turnover mass into the MZR. The residual scatter in metallicity for the global galaxy population around the new FMR is 0.054 dex. The new FMR presented in this work represents a useful local benchmark to compare theoretical predictions and observational studies (of both local and high-redshift galaxies) whose metallicity measurements are tied to the abundance scale defined by the T e method, hence allowing to properly assess its evolution with cosmic time.

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“…Cid Fernandes et al 2011;Belfiore et al 2016), a combination of EW Hα and [N ii]/Hα line ratio (Cid Fernandes et al 2011) or surface brightness of Hα emission (see e.g. Oey et al 2007;Zhang et al 2017;Sanders et al 2017). The fraction of DIG increases with a decrease in the Hα surface brightness of galaxies (Oey et al 2007;Zhang et al 2017 Haffner et al 1999;Voges & Walterbos 2006;Madsen et al 2006;Blanc et al 2009;Zhang et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Metallicity calibrations for diffuse ionized gas and low-ionization emission regions

Kumari

Maiolino

Belfiore

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Using integral field spectroscopic data of 24 nearby spiral galaxies obtained with the Multi-Unit Spectroscopic Explorer (MUSE), we derive empirical calibrations to determine the metallicity of the diffuse ionized gas (DIG) and/or of the low-ionisation emission region (LI(N)ER) in passive regions of galaxies. To do so, we identify a large number of H ii-DIG/LIER pairs that are close enough to be chemically homogeneous and we measure the metallicity difference of each DIG/LIER region relative to its H ii region companion when applying the same strong line calibrations. The O3N2shows a minimal offset (0.01-0.04 dex) between DIG/LIER and H ii regions and little dispersion of the metallicity differences (0.05 dex), suggesting that the O3N2 metallicity calibration for H ii regions can be applied to DIG/LIER regions and that, when used on poorly resolved galaxies, this diagnostic provides reliable results by suffering little from DIG contamination. We also derive second-order corrections which further reduce the scatter (0.03-0.04 dex) in the differential metallicity of H ii-DIG/LIER pairs. Similarly, we explore other metallicity diagnostics such as O3S2 (=log([O iii]/Hβ+[S ii]/Hα)) and N2S2Hα (= log([N ii]/[S ii]) + 0.264log([N ii]/Hα)) and provide corrections for O3S2 to measure the metallicity of DIG/LIER regions. We propose that the corrected O3N2 and O3S2 diagnostics are used to measure the gas-phase metallicity in quiescent galaxies or in quiescent regions of star-forming galaxies.

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Biases in Metallicity Measurements from Global Galaxy Spectra: The Effects of Flux Weighting and Diffuse Ionized Gas Contamination

Cited by 98 publications

References 106 publications

The MOSDEF survey: direct-method metallicities and ISM conditions at z ∼ 1.5–3.5

The MOSDEF survey: direct-method metallicities and ISM conditions at z ∼ 1.5–3.5

The mass–metallicity and the fundamental metallicity relation revisited on a fully Te-based abundance scale for galaxies

Metallicity calibrations for diffuse ionized gas and low-ionization emission regions

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