Chemical abundance scaling relations for multiple elements in z~2-3 star-forming galaxies

Strom, Allison L.; Rudie, Gwen C.; Steidel, Charles C.; Trainor, Ryan F.

doi:10.48550/arxiv.2111.06410

Cited by 4 publications

(4 citation statements)

References 104 publications

(149 reference statements)

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“…An increasing number of reports suggest that such an enhancement is necessary to reconcile the low stellar metallicities relative to the gas-phase oxygen abundance inferred from observations of nebular emission and UV continuum light in massive galaxies at 𝑧 ∼ 2 (e.g. Steidel et al 2016;Strom et al 2017;Sanders et al 2020;Topping et al 2020a;Cullen et al 2021;Strom et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Direct Constraints on the Extremely Metal-Poor Massive Stars Underlying Nebular C IV Emission from Ultra-Deep HST/COS Ultraviolet Spectroscopy

Senchyna,

Stark,

Charlot

et al. 2021

Preprint

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Metal-poor nearby galaxies hosting massive stars have a fundamental role to play in our understanding of both high-redshift galaxies and low metallicity stellar populations. But while much attention has been focused on their bright nebular gas emission, the massive stars that power it remain challenging to constrain. Here we present exceptionally deep Hubble Space Telescope ultraviolet spectra targeting six galaxies that power strong nebular C IV emission approaching that encountered at 𝑧 > 6. We find that the strength and spectral profile of the nebular C IV in these new spectra follow a sequence evocative of resonant scattering models, indicating that the hot circumgalactic medium likely plays a key role in regulating C IV escape locally. We constrain the metallicity of the massive stars in each galaxy by fitting the forest of photospheric absorption lines, reporting measurements driven by iron that lie uniformly below 10% solar. Comparison with the gas-phase oxygen abundances reveals evidence for enhancement in O/Fe above solar across the sample, robust to assumptions about the absolute gas-phase metallicity scale. This supports the idea that these local systems are more chemically-similar to their primordial high-redshift counterparts than to the bulk of nearby galaxies. Finally, we find significant tension between the strong stellar wind profiles observed and our population synthesis models constrained by the photospheric forest in our highest-quality spectra. This reinforces the need for caution in interpreting wind lines in isolation at high-redshift, but also suggests a unique path towards validating fundamental massive star physics at extremely low metallicity with integrated ultraviolet spectra.

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Section: Introductionmentioning

confidence: 99%

Direct Constraints on the Extremely Metal-Poor Massive Stars Underlying Nebular C IV Emission from Ultra-Deep HST/COS Ultraviolet Spectroscopy

Senchyna,

Stark,

Charlot

et al. 2021

Preprint

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“…Analysis of deep spectroscopy of distant galaxies has confirmed this expectation, with significant levels of αenhancement observed in galaxy populations at z ∼ 2 (Steidel et al 2016;Strom et al 2021) and z ∼ 3.4 (Cullen et al 2021). The advent of the James Webb Space Telescope (JWST) extends such analyses to higher redshifts, and such observations make plain the need for stellar population models which incorporate this property.…”

Section: Introductionmentioning

confidence: 82%

The Dependence of Theoretical Synthetic Spectra on $α$-enhancement in Young, Binary Stellar Populations

Byrne,

Stanway,

Eldridge

et al. 2022

Preprint

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The enhancement of α elements such as oxygen is an important phase in the chemical evolution of the early Universe, with nebular material becoming enriched in these elements sooner than iron. Here we present models which incorporate stellar spectra with α-enhanced compositions, focusing on the impact on the integrated light of young stellar populations, including those with large binary star fractions using the Binary Populations and Spectral Synthesis (bpass) framework. We find that broad spectrum outputs such as production of ionising flux, the ultraviolet spectral slope and optical colours are only weakly affected by a change in [α/Fe]. A number of features such as ultraviolet line indices (e.g. at 1719 and 1853 Å) and optical line indices (such as MgB) are sensitive to such changes in composition for a continuously star-forming population and a single starburst population respectively. We find that at ages of more than 1 Gyr, α-enhanced stellar populations appear bluer than their Solar-scaled counterparts, and show expected sensitivity of optical line indices to composition, in agreement with previous work. The ultraviolet stellar absorption lines are relatively insensitive to subtleties in the abundances ratios, although with sufficient measurement precision, a combination of UV line indices may enable a simultaneous measurement of total metallicity mass fraction and [α/Fe] in young stellar populations. The output models produced in this work are designated as bpass v2.3 and made available to the community with the aim of assisting interpretation of observations of high-redshift galaxies with the James Webb Space Telescope.

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“…Currently, there is no consensus on the redshift dependent offset of the mass-metallicity relationship (MZR), or if evolution exists between local and 𝑧 ∼ 1 − 3 galaxies in the "fundamental metallicity relationship" (FMR). In particular, we will investigate the evolution of the mass-metallicity and fundamental metallicity relationships (e.g., Mannucci et al 2010;Sanders et al 2021;Strom et al 2021) using the joint MOSDEF-KBSS sam-ple, enabling the most statistically robust characterization of these relationships at 𝑧 ∼ 2. lines or nebular continuum emission. Following previous studies (Reddy et al 2018;Du et al 2018), we adopt two combinations of extinction curves and metallicity: a 1.4𝑍 metallicity with the Calzetti et al (2000) attenuation curve (hereafter referred to as "1.4 𝑍 +Calzetti", and a 0.28𝑍 metallicity with the Small Magellanic Cloud (SMC) attenuation curve "0.28 𝑍 +SMC".…”

Section: Discussionmentioning

confidence: 99%

Reconciling the Results of the z~2 MOSDEF and KBSS-MOSFIRE Surveys

Runco,

Reddy,

Shapley

et al. 2021

Preprint

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The combination of the MOSDEF and KBSS-MOSFIRE surveys represents the largest joint investment of Keck/MOSFIRE time to date, with ∼3000 galaxies at 1.4 𝑧 3.8, roughly half of which are at 𝑧 ∼ 2. MOSDEF is photometric-and spectroscopic-redshift selected with a rest-optical magnitude limit, while KBSS-MOSFIRE is primarily selected based on rest-UV colors and a rest-UV magnitude limit. Analyzing the two surveys in a uniform manner with consistent spectral-energy-distribution (SED) models, we find that the MOSDEF 𝑧 ∼ 2 targeted sample has a higher median 𝑀 * and redder rest U−V color than the KBSS-MOSFIRE 𝑧 ∼ 2 targeted sample, and a smaller median SED-based SFR and sSFR (SFR(SED) and sSFR(SED)). Specifically, MOSDEF targeted a larger population of red galaxies with U−V and V−J ≥1.25, while KBSS-MOSFIRE contains more young galaxies with intense star formation. Despite these differences in the 𝑧 ∼ 2 targeted samples, the subsets of the surveys with multiple emission lines detected and analyzed in previously published work are much more similar. All median host-galaxy properties with the exception of stellar population age -i.e., 𝑀 * , SFR(SED), sSFR(SED), 𝐴 V , and UVJ colors -agree within the uncertainties. Additionally, when uniform emission-line fitting and stellar Balmer absorption correction techniques are applied, there is no significant offset between the two samples in the [O III]𝜆5008/H𝛽 vs.[N II]𝜆6585/H𝛼 diagnostic diagram, in contrast to previously-reported discrepancies. We can now combine the MOSDEF and KBSS-MOSFIRE surveys to form the largest 𝑧 ∼ 2 sample with moderate-resolution rest-optical spectra and construct the fundamental scaling relations of star-forming galaxies during this important epoch.

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Chemical abundance scaling relations for multiple elements in z~2-3 star-forming galaxies

Cited by 4 publications

References 104 publications

Direct Constraints on the Extremely Metal-Poor Massive Stars Underlying Nebular C IV Emission from Ultra-Deep HST/COS Ultraviolet Spectroscopy

Direct Constraints on the Extremely Metal-Poor Massive Stars Underlying Nebular C IV Emission from Ultra-Deep HST/COS Ultraviolet Spectroscopy

The Dependence of Theoretical Synthetic Spectra on $α$-enhancement in Young, Binary Stellar Populations

Reconciling the Results of the z~2 MOSDEF and KBSS-MOSFIRE Surveys

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